I used to have motivational problems for exercise, especially for running. I'd start doing something and then stop soon enough... I'm amazed that I've spent nearly a year now running or cycling at least 5 days a week. The main trick for me has been to do it first thing in the morning, especially when I have no other motivator. I make sure all I need for either cycling or running is ready the night before (which might even mean putting my bike in my kitchen - our appartment is very small and we definitely do not have a garage!!), fill the water bottles, get the food ready along with my other riding accessories (or just my running clothes if that's what I'm setting out to do). The night before I remind myself a few times, once I'm in bed, that the next morning I am going for a ride/a run and think about the route I'm going to take. Or I talk about it with my sweet partner (also a cyclist, that helps). I guess you can call that visualization.

Then the next morning, before I can think about it, I put on my cycling or running clothes. Once they're on, I feel silly changing out of them, and going out of the door is much easier.

I also agree with all the other pieces of advice, especially the errands. I really enjoy going to the grocery store on my bike...

And above all: smile while you're doing it.