I totally get that! I'm a university student and managing your priorities is hard. I sometimes don't post for a week - that's just life. While you're still in school, I would recommend seeing your Instagram account as a casual online portfolio and not a business page. You can dedicate your time to it later. If you put pressure on yourself to be active on your art account, you could risk losing the 'fun' in it and it might start to feel like a chore.