The best motivation of all is the feeling of succes. Let's face it, in the daily life most of us are just nobodys. If we can scrape together enough money to pay the bills doing whatever crappy work we do, then that's about all we can ask for outside the gym.
Your boss don't pad you on the shoulder and complement you with you good work and your two extra working hours last thursday were just considered something that should be expected if you wanted to keep you job. Everybody takes advantage of you, but nobody recognizes your qualities.
But then you go to the gym...
And in the gym you're only as far from succes as you choose to be. Here you know, that if you just do your best, you will experience that deep, satisfying feeling of having succeded. And you can do it again and again and again...
Every time you improve you BP by just 1 lb, you have achieved something that you have never done before. You are now even better that you were yesterday. And next week, you will be even better! And after having improved on your BP, you will put together a program leading up to adding 10 more lbs to your deadlift in 6 weeks from now.
And during every single training session for those 6 weeks, you can feel yourself working your way towards another succes. It's hard work. Hard as hell. But you can do it, because you've got that feeling of succes in your blood now. Can you feel it now?
And if you plan your training right with a rotation between different exercises, that feeling of succes can be there all the time. Everytime you enter that smelly, crammy gym with the raw concrete walls desperately needing some paint, you can feel it. That feeling of you being fired up and ready to do even better than last time.
So you go for it, and after an hour of hard work, you can sit down with the guys and relax. Talk about the aerobic girls next door, the next Mike Tyson fight or why Arnold is just a whimp compared to what you are gonna look like in five years from now. Because you feel good. Your body feels warn out, but your mind is alive. You've succeded again! Damn, you're still a succes!
That feeling is the best motivation in the world.