I spend the majority of my focus and time on stuff I don't find meaningful. I'm a university student studying mathematics and work part time in buy side finance

I spend the majority of my focus and time on stuff I don't find meaningful. I'm a university student studying mathematics and work part time in buy side finance ~20 hours pr week. I want to work on my startup, but I work most days from 5 to 19 (a little later in weekends) so I can't find any focus or energy to begin working in the evenings on my startup. I'm probably going to quit my job real soon...