As the cliche goes, BTDT. I was going religiously every day or every other day from February 2009 through April of 2012. Then I bought a guitar, and that consumed all of my free time.
Now I'm finally getting back to it. I'm waiting until 11:30 pm, telling myself that I'm done practicing guitar for the day, then head to the gym. I'm just starting out with the treadmill, but will go to the weight machines.
Don't know about you, but if I find myself not wanting to go, I really force myself. I take the same attitude about it that I would any other chore I do that has to be done, and that I do.
I had some outside stimulus, though. I was in an amorous situation, and the young lady said, "boy, you're really sweating." That was the signal for me to get my butt back to the gym.