Well, I know some people are turned off by the suggestion and that's fine, but this has worked for me and given my a fun, varied, and fulfilling life so far: What do you suppose God wants you to be doing? Do you have any special abilities or talents that you can use to make a living, contribute to society, and have fun?
I believe that there are certain things we are called to do, and that happiness is most reliably achieved by figuring out what that is and pursuing it with all your heart. If you really don't feel any kind of special calling, then use your youth and initiative to experiment. At 20 years old, you already have one gift right now, that gift is time. Time to look for opportunities that you think may interest you and that you may be talented at, and time to try as many as you can. Apply the highest principles and standards to yourself as you can in all things, stay focused on figuring it out, and you will always succeed in whatever you try.
Again, I try to listen to the Lord and heed His call, somedays I am much more successful than others! If you are one who believes in God, He can and will help you in finding your niche.
Good luck!