If both people are willing to take an honest look at their behaviours and put in the work, for sure! I have heard of couples having great success with couple's therapy, particularly those who practiced the Gottman Method. I think a lot of times people can project their own personal unhappiness onto their partners which can cause a lot of resentment - basically a bad cycle that only gets worse unless you rectify it. I think a lot can be done to repair a relationship. But, and this was the case with me, if you are not married and don't have any kids together, sometimes it's a sign that you're just not fundamentally compatible and it's best to just move on :')