Hello there,
Well all have a common motivation on this forum, to get fit and lean. That feeling when you finish a workout and the hormones are rushing though your body, giving you a feeling of euphoria. This is one of my favorite sensations (That and a nice, healthy, filling meal), but sometimes there are days where you just don't want to do anything. I admit I have had a fair few the past few months due to stress and seasonal depression, but I always looked back on my own way of motivation.
I love good music and one way to get me going is music that makes even the most mundane task seem like an epic quest. The feeling is enhanced when I am at my local gym, doing my routine. I have many artists I listen to, but the one that does it for me by far must be Two Steps From Hell.
Please, post your own way of keeping motivated. hopefully it will inspire other users to try your method and help them along their journey.