How to decide if something is financially worth your time?

I have a primary business which provides 70% of my income and some tangential businesses that contribute 30%. One of these tangential businesses takes up a lot of time and energy and only provides 4.8% of my overall income. I’m thinking I need to exhibit some constraint in order to focus more creative energy on my primary business and say goodbye to the 4.8. Any questions or considerations that could help me confidently make this decision? I’m still holding on to the 4.8 because it does still contribute to my overall financial goal for the year! Thank you in advance!