ghosts that changed us:The question ?

We all wish we could change our past,not realizing that it has already succeeded in changing us,with every experience we lived,with every action we did,our mistakes changed permanently how we are going to live our life.we only realize that at certain times.
Whenever we experience a repeated situation from our past,fear kicks in we feel afraid of suffering again like we suffered before, by doing the same things, or doing the same actions that we did before.That fear itself normally results in much more mistakes because trying to avoid making previous mistakes -believe me - might end up with an even worse results.
The question is ,which is actually not an easy one ,Should we let our past cause us to live in fear,fear from ending up in suffering or losing what we lost before ,or should we forget and ignore our past ,risking doing more stupid mistakes that add up to our previous ones causing us more fear and suffering???