"Lazy" is such an emotionally loaded word? Where did you get your personal definition of what is and is not lazy? Your lovely mother! What do you have if you decide you don't want that? Nothing?

Can you go a bit sideways and say you were "not interested" in doing school work? That takes away the could-but-deliberately-did-not-for-spite and puts it into the could-but-it-did-not-interest-you category? A very small change but gives you some control over what you want/interests you? I realize that you could have been unconsciously battling the mother by not doing better (my case) or you could have been overwhelmed by the mother so you could not do the work at that time, but I think the branding of "lazy" makes it too static/permanent and set in cement in the past where nothing can change or be thought of in a better way. If you "are" not interested, you can become interested at any time in the present/future. If you are "lazy", maybe you will learn to work hard and not be lazy anymore but that feels different; like trying to get moving from a complete stop rather than rolling along through the years and just deciding to accelerate from not interested in something to being interested in something.

Lazy says you did not try. So does "not interested". Why think of yourself so negatively since it is you thinking of you? It is a little like worry for me -- it is all in the future and we can't know the future so why not think positively about it rather than that things are going to go wrong. It allows a personal decision, how we want to think about it, since what is going to happen is not known yet. Your mother decided you were lazy, that her word should describe you, but you can make a decision to think of it some other way because it is about You and your mother is not you.