There are many reasons to procrastinate and most procrastinator's will use every one of them.

Sometimes it comes across as lazy or unwillingness to take action.

I think a lot of it boils down to fear.

We are motivated by pleasure and pain, we tend to move towards pleasure and away from pain, that is why it is so so important to find a positive reason to do what ever it is you want to do.

If you can find a big enough positive reason you can achieve anything.