(i realize we are not adults but i figure adult would have more experiences)

i was dating this guy for a very short time and i then i broke up with him. im not one hundred percent positive why, i think it had something to do with everyone putting in their opinions and it was my first relationship so i know it sounds childish but i kind of expected it to be like the movies. but as soon as i did it i felt bad he’s such a nice guy and really good for me he makes me want to better myself. but im unsure if i should try to fix things or not. any advice?