It's hard to incorporate exercise into a busy day. The only thing that worked for me is to do it first thing in the morning. When I get up, I put on my workout clothes. That's half the battle done. Then my subconscious self says "Well, since you're dressed..." I just do it.

I really like short workouts typical of HIIT (high-intensity interval training). They are short, effective and easy to fit into the day. Some are as short as 7 minutes. Typically I do 20 minutes. Don't let high-intensity put you off. You only do the intensity level that suits you. Low impact counts too.