I always go to the gym at night, around 8:30pm MWF.

I've been trying to figure out why some days I'm strong, and some days just so so.

A couple weeks ago I went out to lunch with the guys from work. I ordered pad Thai, extra chicken, and ate the whole thing. I felt irresponsible  for eating so much. For dinner I just had a very small meal of chicken/rice/broccoli. Well, that night I was very strong. It was one of my best nights ever. I'm starting to wonder how much a strong workout has to do with my eating that day. Timing, quantity, carbs, etc.

Anybody notice patterns like this?

Food affects me very little, how my day went is huge though.

If it was a hard day, even just mentally difficult, I can't stay as focused.

If it was a physically hard day (and they are frequent) it's all I can do to complete the warm up sometimes.

If your glycogen stores are full when you hit the gym, you’ll be stronger. (Big lunch scenario)

Depending on your goals, working out in a depleted state and then hitting the food hard after can have significant benefits.

You don’t want to eat dinner then hit the gym.

Of course, diet and timing matter.  This is something everyone should know.  Diet is probably the biggest factor along with sleep.  

Here is what you need to know...

Macro nutrients and total calorie intake matters most.
Micronutrients matter, but less than macros
Timing matters, but less than Macro or micronutrients.

...or you can listen to a PhD talk for several hours and tell you the same thing...LOL

My coach recommends eating my preworkout meal 1 hour before lifting.  It's the same every day which is 40grams of protein from whey isolate, carbs (varies in amount depending on my current goals and whether its a normal or high day) from gerber baby rice cereal, and 100g blueberries.  

Post workout meal is a bowl of cereal with 1.5g or less fat per serving.  That's my favorite meal it's usually frosted mini wheats, raisin bran crunch, or captain crunch.  The amount of carbs varies depending on if it is a normal or high day and if I am cutting or bulking etc.  On high days its so much cereal I have to use a ramen bowl to fit it all.  I eat it with unsweetened vanilla almond milk.  Also 60g protein from whey isolate with 3g HMB, 5g Creatine, 7g leucine.

Whatever you decide on I would recommend fast digesting carbs before and after working out.

Surprising a professional coach recommends relying so much on protein powders and cereals like frosted mini wheats and captain crunch.  

Not saying he's wrong just surprised.  

I barely use any supplements or protein powder and get all of my protein from eggs, beef, chicken, and some bacon when I want a treat...lol.  I like drinking milk too I love the stuff mmmm.  I could be doing it completely wrong though since I've never had a professional coach.

I find that whey and some carbs an hour before the gym can make me nauseous sometimes, especially on leg day.

I eat 6 meals a day.  My pre-workout meal and post-workout meal are heavily focused on using the fastest digesting carbs and protein possible.  The rest of the day is whole foods.  Meal 3 is chicken, rice, hardboiled eggs (can make them any way but its convenient).  Meal 4 is the same as meal 3.  Meal 5 is top round steak or 96/4 ground beef, sauerkraut, and potatoes.  Meal 6 is top round steak and a vegetable mix sautéed in olive oil.  I have veggies with usually 3 of my meals a day but never with my pre or post meal.  I was eating salmon and sweet potatoes as meal 6 but im on a cut so my fats went down so the salmon is out for now.

The pre and post meals can be any part of the day but i am supposed to eat those right around my workout.  The idea is fast digesting carbs before to have that fuel ready and fast digesting carbs after to refill glycogen stores.  

Since I've started doing this Ive had a few people tell me they eat cereal post workout as well and one was a lady who competes and trains clients.  She doesn't look to have an ounce of fat on her lol.

I eat 6 meals a day.  My pre-workout meal and post-workout meal are heavily focused on using the fastest digesting carbs and protein possible.  The rest of the day is whole foods.  Meal 3 is chicken, rice, hardboiled eggs (can make them any way but its convenient).  Meal 4 is the same as meal 3.  Meal 5 is top round steak or 96/4 ground beef, sauerkraut, and potatoes.  Meal 6 is top round steak and a vegetable mix sautéed in olive oil.  I have veggies with usually 3 of my meals a day but never with my pre or post meal.  I was eating salmon and sweet potatoes as meal 6 but im on a cut so my fats went down so the salmon is out for now.

The pre and post meals can be any part of the day but i am supposed to eat those right around my workout.

I eat a LOT of chicken every day.  It gets old.  I cook a huge costco bag of chicken breasts every weekend.

OP, if your goal is to become bigger, stronger and you're not an old guy like me, then I'd go with ds3_09's post. It's spot on imho!
Especially his mindfullness of not taxing your digestive system right before or after your workout will probably fix your issue.
As an old guy I frequently work out fasted. That has it's own benefits but for different goals.

I'm not saying you're wrong it's just interesting what your professional coach recommends.  I eat 4000 calories a day and I'm a little dude no issue staying lean.  I eat healthy for the most part, but I can eat whatever I want so nothing ever gets old.  Even at 48 years old and natural no trt or anything.  More than one way to do things digestion is never an issue for me.  I can drink a ton of milk or eat huge amounts of anything and work out immediately after.   Maybe I'm doing everything wrong I don't know never had a coach...LOL.

I don't think you are doing anything wrong.  I made good progress on my own but I have learned a good bit from the coaches I have used.  I feel like with this coach I've really got all my gears turning and have had improved performance just following his nutrition and lifting advice.  He definitely knows more than me.  He has his pro card and his only job that he makes a living on is coaching people and he is supposedly the very best in the area I live.

As far as eating before lifting the only issue I've ever had is when bulking I would eat a MASSIVE bowl of oatmeal and then do deadlifts half an hour later.  Every time I would feel like I'm going to hurl.  Other than that I've eaten some massive waffle house or ihop breakfasts right before lifting and felt fine as long as I'm not doing deadlifts right off the bat.

I think there's lots of right ways.  There's probably wrong ways as well but that doesn't mean I think anything different than what I am doing is wrong.

Consistency is really the key.  Work hard enough consistently, get good sleep consistently, hit your daily macro and calorie goals consistently.  Over time consistency will lead to great results.  I don't do bulk/cut I stay relatively lean all year round without ever trying to get super crazy lean.  I can also eat foods I enjoy whenever I want and have visible abs all year round so, I'm plenty lean enough.  I'm more into power lifting, but doing it without looking like a stereotypical power lifter either lol.

I forgot to put that I also like to add almond butter to the whey isolate and Gerber baby rice shake.  I just don't get to right now since I'm working on getting leaner right now.  Adding the nut butter makes the shake tastier and creamier.  It's kind of bland without a little fat.