Find what motivates you. For me - I like to watch "money tv" or listen to music. The first because it keeps my brain away from the pain and focused on "something else." The second because the beat and sometimes the words really help me stick with a tough routine.
My FAVORITE song to workout to is Eminem's Lose Yourself. I play this whenever I am trying to do something really difficult.
It's not just the "tear this mother f.. roof off like two dogs caged" that I like about this song. I love the beat and the message - "you only get one shot, do not miss your chance....this opportunity comes once in a lifetime." It makes me stick it out and push harder.
And it's also a good life lesson. You only get one shot - make the most of it. Find what work for you and stick with it!