Might need a little context, but most likely I was enjoying myself instead of working . I was too short to reach the high self. I was eating too much to be thin. I was enjoying myself too much to work very hard. I was <something> too much to <another something>. ==> Not <something> and yes <another something>

It means 'I was enjoying myself instead of working.' It's a thing people might well say to excuse poor exam results or other performance. A bit like "If you remember the sixties, you weren't really there." https://quoteinvestigator.com/2010/05/07/remember-1960s/