Don't be confused by false happiness from memories, your mind has a way of tricking you.
If you find yourself missing them, remind yourself why they're in your past.
Don't let the memories from the past contuine to haunt you today, you conquered them already.
If a dark memory arises from the past, think of a positive from the same time.
Don't dwell on past recollections, you are ruining today's happiness.
Acknowledge the feelings associated with these memories, but don't let them stay, feel them, then turn away.