Motivation vs Laziness

I realize that I have a lack of motivation when it comes to a lot of things. At the beginning stages of a project, I get excited and am full of ideas. But soon, the novelty wears off and I don't follow through. How do you stay motivated?

Here are my current "projects" that I'm excited about along with concerns:

1) I'm starting school next month and want to pack lunch at least 3 times a week rather than eating out. This is both for monetary and health reasons. As a student, I definitely will not have the funds to be eating out daily. Also, I'd like to do some portion control as well as eating more healthy food. Though I'm excited about the possibility of things to cook, I already feel unmotivated for various reasons... time, energy, laziness.

2) I started swimming again a few months ago and this is something I'd like to keep up. I feel healthier and more energetic than when I wasn't exercising. Once I start school, realistically, how often will this happen?

I don't know if it's motivation that I'm lacking or if it's that I have too much laziness and too many excuses. Hm...