Think of relationships of any description, be they platonic, romantic, even professional, as a mutual connection that should bring you joy, inspire and uplift you and make you feel good about yourself. By that I'm not saying the person is responsible for your happiness, but by them being who they are, it should flow and 'hangs together' effortlessly, while you are both investing in that relationship.
If you find yourself constantly wound up, feeling downtrodden or ill at ease in that person's presence, then take that as the indicator that you need to extract yourself and go in pursuit of relationships that fulfil your, and their, mutual needs simultaneously.
Couple of examples (remember, all relationships should operate to the above same principles) :-
I had a truly dire relationship with the manager I was working for, some time back. Everything about it was wrong, wrong, wrong. I lost confidence in myself and they chipped away at my spirit. Yet to another person in their team they were wonderful, encouraging and supportive. The chemistry was wrong. I went on to a new job and I'm riding on the crest of a wave, because the person wants me in their crew and likes what I do (my confidence is self-perpetuating due to their confidence in me).
I had to walk away from a friendship because, although it was promising to begin with, I realised over time that the person did not "have my back", they didn't have my best interests at heart. The day I extracted myself from that relationship I felt the weight of the world had been lifted from my shoulders. I felt empowered and in control of my life, because I made the choice that was right for me and my happiness.
It is no different in a romantic relationship. If you're with someone who you are constantly in conflict with or where it's a rollercoaster of good one day bad the next, it becomes exhausting and wears you down. If you feel better apart than you do together, that's a big red flag you need to take seriously.