I do have issues of motivating myself to do anything and usually for me if I ever do get any sort of motivation it's most likely from an external source.
Since I've started admitting my romantic feelings for her I have embraced the phrase "Do it for her" in it's entirety. Not exactly the greatest nor healthiest motivation but I'm more active than I have been in a while.
Due to my new founded reason for trying along with it came confidence and pride.
How I look of it is that I want to be able to stand with her and have her be proud of me and my accomplishments. I suppose I really just want to prove myself to her.