First step is figuring out why your relationship is broken or not working. There is a reason behind this. It could be that you don't appreciate all the little things that your partner does or you may have gotten involved with someone else and there needs to be fixing. You may have hurt your partner in a way you may not know of or just not give them the respect that they need right now. You must figure out what it is that is not making the relationship work, like, key pointing the infection that way things can be resolved.
You will never be able to change the past, have to accept what has happened whether good or bad, but what you can change is the future ahead. You must commit to making the relationship better, and sticking to it. If you love this person and care about them, the bad can be fixed it just takes time and understatement. Fixing the relationship must be a priority before anything else can get better, if it is not fixed than things will just go back to the same old ways. You have to put in the work to rebuild the love and affection, it does not come at an easy price. In other words you have to commit right now that you want to make the relationship better, not just one person but both.
The hard thing is being able to forgive your partner and the person who has done wrong to forgive themselves, but we must forgive and move on. But since you have decided to make your relationship a priority. You have to focus on the healing part. By letting the past be the past and focusing on the now, and the present and future relationship. If you hold on to any old pain or grudges it wont help the relationship at all and it can just make it worse, you must start at a new.
Lastly you have to communicate with one another. If there is no communication the relationship just wont work. You have to tell them that you love and care about them and that you really want this relationship to work out. Fixing a relationship isn't hard, it is just a matter of time, and being patient. Everyone heals at their own rate, but we also must reassure that we are committed.
Hopefully some of this helped out. I cant really say much, but like I said it is just always nice to know that you are not alone.
Good luck to anyone out there!!!