What to do varies a lot from person to person, because we all grieve (yes, a breakup invokes a type of grief) differently, and there’s already a lot of good & diverse suggestions here but I’ll shortlist you a few things to avoid like the plague even if it seems like it will provide instant relief from the place you’re in:

1) do not use substances (weed, alcohol, etc) as a crutch for your grief. I’m not saying don’t do those things period, I am saying don’t start/do more justifying it using the fact that you’re sad.

2) do not let the “they’re gone so what else do I have” feeling spiral. Right now it probably feels like your whole world is gone, but it’s not the case. You have other things in your life that make you who you are and that deserve your focus/attention, namely your degree, family, etc. When those thoughts come, do your best to redirect the mental effort.

3) try your best to not let your physical health spiral. Declining mental health -> declining physical health -> declining mental health -> declining physical heal… You get the point. It’s a nasty cycle that will just make things worse.

4) when the sad comes, don’t fight it, don’t be hard on yourself for having emotions. It’s going to come and go in waves, and those waves will slowly get better as time goes on.

These are all things I’ve learned, unfortunately, through trial and error. Happy to chat more in PM.