I've got a pretty bad (even with proper treatment) case of ADHD, so I'm either doing everything at once or nothing at all. I tend to sit and stare and daydream about the projects I want to work on, and that can be detrimental as it sometimes gives me the small dose of dopamine associated with "reward" and "completion". So instead of working on and competing a project, I'll feel like I'd already done the work. So I never get anything done.

The best defense is a good offense. Remind myself that I haven't earned any rewards, and dedicate time to working on it - even if that means working while I watch TV where I'm not using my full concentration.