Asklemmy

As a highly sensitive person, what I've learned for me is:

1. It takes time - years, even - to understand what happened, and why. Which means there's nothing productive to be done except avoid things you'd regret. Be your best self, even if it's hard as hell. If you care about this person, give them the space they evidently need; and leave the door open to reconnecting later in until you've decided, with a clear head and understanding why, that you'll never eant them in your life.
2. Prioritize caring for your basic mental and physical needs by getting enough sleep, food, exercise, and time outdoors.
3. Treat yourself like you're sick with the flu or a cold. Get rest if you can. Find ways to relax. Give yourself time to heal. Mindless things like TV or videogames can be good. Socializing is also good.
4. Partners can ground us; make us feel secure, taken care of, connected to our world, full of purpose and value, etc. In the long term, without them, you need to re-ground and find things that give you those feelings. I had to come up with a list of things that make me feel connected and worthwhile, then take steps to engage in those. It included creative hobbies and dedicating time to good friends. Finding "myself" and things that felt meaningful took work: self-reflection and journaling, forcing myself to do hobbies until I enjoyed them, and becoming inspired by good art (TV, music) I love. Often our roots are in our upbringing, so it can be good to reconnect with things we loved. Once you have a life without your ex, you don't need them. You don't need any partner as much, for that matter, because what sustains you is more within your power and identity. And that's how future relationships can be made safer, and heartbreak survivable.