Compulsive selecting while reading, and hitting CTRL+S every couple seconds while editing documents, are the two "weird" habits I couldn't kick for decades now. Most of the time, I'm not even conscious I'm doing those things; I only notice when the text isn't selectable or the program pops up a modal in response to CTRL+S.

Developed this habit as a kid on a Mac IIcx in 1992. Hard to break.