Manual saving. I got so used to auto saves over the years that now when I go back and play older games I find myself going absurd spans of time between saves, whereas growing up I habitually saved after everything I did.

Also, I find insane levels of grinding hard to deal with now. I don't mind moderate grinding, but like, I told myself I was going to get the platinum of FFXHD, then I realized you needed to complete the monster arena, get Wakka's sigil, and max out the sphere grid and I did everything else except those three things and gave up.