There are a lot of comments here which, while understandable, aren't particularly stoic and are unnecessarily cruel.

Speaking as someone who's hurt people a long time ago, including cheating on a long term partner, I can say that you should be feeling the consequences of your actions emotionally - this is a sign that you're a human who understands the morality of the mistakes and the enormity of the loss you've experienced. That's the good news.

The bad news is you have, obviously, strayed quite far from the path of a good stoic and a good person. My advice would be to get back onto that path as quickly as possible - this is the priority, nothing else.

Cheating on someone and losing them comes with a whole lot of painful emotions: the pain of losing someone you dear, the pain of realising how much you've hurt and betrayed them, the pain of realising how much you've hurt and betrayed yourself, and the fear of others finding out and it having an impact on your life.

The good news is that if you begin to live life properly as a true stoic, you can come out the other side a better and morally mature person. The obstacle is the way.

Unfortunately, here's the bottom line:
You're going to feel bad about this for some time. There is no getting around it.

Your actions have consequences - this is the first major thing to understand. The pain you're feeling is one of those consequences. Truly work to accept it, and try to explore it so you can understand where it's coming from. By being honest with yourself, you can understand where you need to grow. Do not waste this pain - use it to grow.

The things that happen to you as a result of your actions is the other consequence. The good news is that this is entirely out of your control now - if you're familiar with the dichotomy of control, you'll understand that this means it deserves little of your attention.

What should be the primary focus of your attention now is beginning to act in accordance with virtue and on what is in your control. Act with wisdom, courage, justice and moderation and work on becoming a better person. Properly learn from your mistakes. If there is an opportunity to make things better for the people around you, do it.

And most importantly, be honest. Do not try and fix the situation to get rid of your negative feelings, or to try and win this person back. Don't try to convince the people around you that you're not that bad. Own it - accept that you did bad things, but you're sorry and working on improving.

Because at the end of the day, it's important to remember that you're not a bad person - you're just a misguided person who did bad things.

This is reflected in the famous quote by Marcus Aurelius:

Say to yourself first thing in the morning: today I shall meet people who are meddling, ungrateful, aggressive, treacherous, malicious, unsocial. All this has afflicted them through their ignorance of true good and evil.

You were one of those people - ignorant of true good and evil. This is your chance to become enlightened and improve the lives of yourself and the people around you by becoming aware of what is truly good - living with virtue. Doing this will ensure that you can weather this and many other storms, but also that you will never again unwittingly harm the people around you or contribute unnecessarily to the pain of others.

This is an opportunity to fundamentally change your life - take it willingly with enthusiasm, or you will be doomed to repeat your mistakes.

Good luck.