Breaking the cycle

Does this sound familiar to anyone? I'd love some advice.

I set myself a goal; I get excited about it; I feel positive and motivated; worries start to niggle at me; I struggle to work out where/how to start; I procrastinate; I get stressed about how long I've procrastinated; I don't get anywhere; I don't go to bed for ages because I sit up worrying about what I haven't achieved; I try again the next day and repeat the same cycle.

Anyone know how to break that cycle? I'm so sick of procrastinating - it's holding me back!