I have the same problem – I seem to have a OCD-tendencies coupled with a short attention span that makes it very, very difficult to apply myself to any solid discipline or work.
The areas where I’ve had the longest-lasting success was with my diet, wherein a few years ago I frequently had fast food, junk food all the time. I’ve completed eliminated soft drinks from my diet, have chain fast food maybe once a month, and now more than 80% of my food is freshly prepared food which is generally far healthier. I haven’t lost any weight but that wasn’t my goal; it was to have a healthier lifestyle.
The way I did that was to just completely dump any larger ‘diet’ plan, eating schedules, substitutions, or anything like that. I just picked one small item and eliminated it from my diet. I started with Coke, then all soft drinks, substituting them for juice (100%) and felt great. That lead to going from the ‘bad’ fast food like McDonald’s to slightly healthier chains like Subway, and now I prefer those uppity organic whatever salad bar. I just started with one item, did it, then moved to the next, and at all times you’re just concentrating on the one change because once you’ve changed that small habit it will reinforce itself.
Don’t think, do it tomorrow. Pick one thing, like cancelling burgers from your diet. Doesn’t matter if you go to fish & chips – you’ll get to those in time.
Or stop buying something small that is a waste item, like chips (saves both your health and money!)
Quitting smoking is hard, but it’s the same approach. Pick one thing that compells you to smoke, like just stop smoking at lunchtime.
Just pick a small thing that gets you closer to your goal. Don’t think, just do it. Once you’ve mastered that change, move onto the next thing. Only look at the next small step, don’t worry about the bigger plan – start planning when you don’t have anymore changes to make and you’ll realise you’re already a lot farther along then you think.