When I started cutting, it was just a small cut here and there. It only goes downhill from there. My body got used to those smaller cuts, so I ended up with larger and deeper cuts.
I swore I would never get to that point, but when cutting is used as a coping skill, at that point when the cutting feels necessary, it doesn't matter what we tell ourselves. You just don't think about all the consequences, until it's too late. You have a large cut, you need stitches, or worse...

Basically, my point is, you may be planning on small cuts, but it doesn't always turn out that way. It's really important to learn other coping skills.
(I went through DBT which helped a lot, but I still do have the urges to cut, and occasionally do cut, but it's not like it was before)