I know that problem, and what I've found is that it helps if I break the task down as small as possible. Instead of "I have to write an application," just "I open the file and write the heading" - and then often the hardest part is done and things move forward on their own. The mental hurdle to get started is the worst part, not the task itself.
What really made a difference for me: creating external structure. A fixed time, a fixed place (even if it's just the kitchen table), and then you just go - no negotiating. And this is really important: if it doesn't work out, don't spiral into the "I'm lazy and have no discipline" thing. Some days just suck, and that's okay. It's about consistency over time, not perfection every single day.
I wouldn't just ignore the psychological side of things (fear, perfectionism). If it applies to everything - school, everyday stuff, doctor's appointments - it might be worth talking to someone about it, not to get labeled as "wrong" or anything, but to understand what's really going on. Sometimes procrastination is also a symptom of something else, and dealing with that helps more than any time-management trick.