Not sure how deeply positive it was necessarily, but as far as I can tell I changed at least one person's life significantly.

When I was in middle school I learned how to solve the Rubik's cube through online tutorials, and afterwards I was basically addicted to it for a while and I was messing with a cube all the time. One of my classmates was interested in learning how to solve one, so I drew a bunch of guides and taught him the terminology, and soon enough he was also hooked on the Rubik's cube.

I eventually grew tired of it, but he kept going and learned how to solve all sorts of smaller and bigger cubes and pyramids. I bumped into him at uni a few years later and he had a cube in his hand lol. Last I heard of him he was even participating in some local competitions, but idk what he's up to now.

Even if he ultimately gave up on his speedcubing dreams I can at least say that I introduced him to a cool new hobby that kept him entertained for several years.