As many others have said, wear them and train with them often.  Your body will get used to them and for every pound of body weight you shed they will get lighter too.  

That's a badass pic man!  I sell tractors...LOL

Just Imagine how many more tractors you would sell if you were wearing a PC.......
Farmers appreciate Bad ass as much as the next guy.....

Aside from the fitness, it's probably just from being an old bastard OP.

Two steel plates, a carrier, a FAK, 3 rifle mags and a rifle comes in at around 30 pounds.  In the grand scheme of things, that's not much.  If the weight is dispersed comfortably, you probably won't even notice it.

Try moving shit around, ditch anything other than 3 spare rifle mags and a FAK unless you are doing special stuff like training with a group and need comms.

A comfortable 30 pounds feels like you ate a nice steak dinner and wore an extra layer if you're wearing it for a short period of time, like an hour.

Lol! This. Ain’t no getting around it OP, plates suck! And sometimes they SUPER SUCK!

Plate carrier w/o side plates for the win!