You might want to act like the breakup doesn't bother you, but don't let your pride stop you from being honest. You don't have to cry at work, but you should take some time to yourself to think and be honest. It's fine to be mad, hurt, or embarrassed.
Set aside some time to be alone and let yourself feel sad about the end of the relationship. If your ex wants to be friends with you and you don't feel like it, don't give in. You don't want to find a friend who looks just like the person who broke your heart right now.
The thrill of getting even only makes people more angry and hateful. Even if you've been hurt very badly, "getting even" won't make things better. Just let it go and move on. Keep your head up and give your time and energy to people who need it.
There are times when it will be important to talk to an ex. You might need to give him back his things. You might have to deal with a shared lease or who gets to keep the pet. But resist the urge to call or text as much as you did when you were dating.
Yes, it's okay for dogs to beg. But you can't. Maybe you don't know why it had to end. Maybe you think it should not have ended the way it did. You might just rather be in a bad relationship than have none at all.
Don't do it. No woman ever says on her deathbed, "I really wish I had one last sleep with my ex-husband." Let there be no mess.
When you're going through a hard time, social media can make things worse. Set two rules for yourself: don't post anything online about the breakup, no matter how vague, and don't stalk your ex.