association

I noticed today as I drove away from home to go to work that I felt like going to work. Now if you had asked me an hour or so earlier if I felt like going to work the answer would have been no.

What happened in between?

I took a shower and got dressed in my work clothes that's all.

And therein lies a clue to success.

We associate things with each other, we do it naturally, don't even notice most of the time. We associate the words we use with certain things, we associate the clothes we wear with certain things and we associate the direction we drive with certain things.

Don't feel much like exercising? Put on your exercise clothes and you will find it easier to change your mind.
Don't feel like practicing the guitar, pick it up and tune it.
Don't feel like working on the car, open the hood anyway.

Pay attention to the things around the activities you want to do. When the day comes that you don't feel like doing something anymore then go through those preliminary steps that you had always done before and see what happens.