Long term motivation is difficult. Without a clear set finish line it's hard to get up and push yourself on a daily basis. Abstract mountains are harder to overcome than clear cut molehills. Sit down and define not just what you want to accomplish, but why you want it.
Keeping motivation consistent is where it gets tricky. Everyone has a method, find what works for you. For me, there is one person that even the thought of her pushes me(it's a long story). I get three email reminders a day that say "What if you saw her today?" "Are you working towards your goals or just talking about them?" "Would you be infuriated, embarrassed or proud if you had to bare raw your work/fitness/life?" These notes are everywhere. My cellphone, my gym playlist, my work desk, my wallet. Anywhere I might need an extra reminder or slight kick in the ass.
Collect the things that inspire you to push past your limits. Whether it's a song, a picture, or an argument with an old friend(once again, LONG STORY).