Something that I've learned from Hubski is that success and failure are granular. You succeed or fail moment by moment, and most of the time* a grain of progress more than offsets a grain of failure. There's also a lot to be said for momentum.
I think this is where my problem lies today. I've been sick for a couple days, so I lost all my inertia, instead sitting around and watching Friends all the time. Now that I'm getting better, I find it's tremendously difficult to start doing things again.There's also a lot to be said for momentum.
The way I try to regain my inertia is to start with some small tasks that I know I'll be able to do in ten minutes. Clean dishes. Take out the trash. Write a paragraph. Do a three or four of these small tasks in a row - they'll give you the satisfaction of having accomplished something useful. Then, take a break, get some coffee, and do two or three tasks that take a bit longer. You've now had an hour of productivity, which for me is more than enough inertia to keep on going. Starting is the hardest part, so make that easier.
This is what kills my workout streaks. I'll go a week or two of solid workouts, every other day maybe, get sick or get symptomatic (Heart stuff) and have to take a few days off, and then my momentum is gone, and I'll go weeks without working out. When I'm sick now I make a point to catch up on reading or audiobooks, so I at least feel like I did something.