How do you cope when you find out your ex is seeing someone new?

If I still have feelings for them, I cry. You have to get the crying out of your system. Then, to get yourself to slowly stop thinking about them, tell yourself you're happy for them. Maybe tell them you're happy for them. Find a hobby or take on more hours at work or pamper yourself, make yourself feel good. Focus on bettering yourself. Eventually, you're not even worried about what's going on with them.

There really is no black and white answer here. No right or wrong way to cope. Maybe your incredably sad, that they've moved on without you, or angry that they are with someone who isn't you, maybe your happy that they've found someone again. However your feeling- Your entitled to feeling that way. Your allowed to feel however you feel. Always own your emotions, accept them so you can ultimately move forward.

It hurts at first. Although you are no longer with this person, it still feels like there is a sense of trust that is broken especially after being in a relationship with them. I always go by the saying "What's for you will not pass you", so if they are moving on, it means that it wasn't meant to be and that you deserve to be happy, regardless of who they are seeing.

You let go, cry do what you need to do .. and think too yourself that you deserve better , there will be better

What I did was listen to applicable music. I find that music helps you to express emotion. I would listen to "Irreplacable" by Beyonce for example as many of the lyrics highlighted what I'd been through in our relationship but at the same time, it offered the empowerment I needed to carry on.