In your pursuit of fitness, motivation is everything. It's easy to learn the movements, it's easy to pay a membership and show up consistently, count out your reps and go home; but finding the drive to perform WELL, like you actually care, that takes motivation. I see it all the time, people just going through the motions and putting no heart into their workout. Maybe they're happy with mediocrity, but I'm not.
Figure out what motivates you. I like to think that someone who is paying what CrossFit charges per month is already on the right track. You must see some value in spending the extra cash. Move on from there, ask yourself some questions. Ask yourself the most important question: WHY DO I TRAIN? If you can't answer that then I can't help you. I've asked that question to many people in the past few years, and I rarely get a good answer; but the worst is no answer. I'd rather hear a stupid answer that's truthful than get a shrug and an, "I don't know," response. Chances are that the truthful person is going have some kind of motivation to go with their answer.
Motivation from outside sources is powerful, but it doesn't come close to the power of self motivation. Once you can find your drive and harness it, you will not only become fitter and become a more effective athlete, you'll develop a mental toughness stronger than anyone else.
At the end of the day, a 20 minute AMRAP will always be 20 minutes, regardless of your performance. Why not strive for your best?