Take up a hobby you've been wanting to, or travel somewhere you've been wanting to go. A change of scenery, or a new hobby to fill the hole left by the person who has left you, can be helpful in healing.
Do you wish to stay in the marriage? If yes, then know that you can save the marriage if the cheating partner has acknowledged his mistakes and wants to change it all. Go seek help of a professional counselor NOW. There are many benefits of seeking marriage counseling