Good for you for telling your story here on this forum. When you wrote about intending to get some exercise every day, but can't seem to stick to that plan, it reminded me of a time when I thought to get up every morning at 6 a.m. to ride my bicycle - but I only did that about two times - then gave up on that plan. Maybe it was with the realization that every day was too intensive - so perhaps a better plan would have been maybe two or three times per week instead. I guess what I'm saying is take smaller steps and gradually get there. That way you can congratulate yourself for each small step, without scolding yourself for not following through with the "daily" stuff. Eat healthy - try to follow the food guide. For the cutting - maybe try to think of some alternatives (or even use some of those cut pieces to make art).
For the computer use - a method that I used (and this worked for me) - I decided that I should only use the computer for research and the occasional email - so I closed the computer and taped a note on it to remind me of this "research only". Then carry on with my day (as I had before computer ever entered my life - there was my life before computer).