Mental Block on Positive Thoughts?

A mental block is an informal term used to mean either repression of painful thoughts, or an inability to continue a train of thought, like in the case of writer’s block.
Today I was pondering the power of “mental blocks”. You know, the times when life’s events are so painful that our brain manages to “block” them from our memory?

An individual close to me reminds me of “mental blocks” when I express surprise at their lack of memories about some events. I’ve often wondered if they really repressed the memories, or if that’s just their way of saying “I don’t want to talk about it.”

For some reason, though, I got to wondering if it was possible to have mental blocks where you repress good things rather than bad. Does your brain ever block the happy times and only remind you of the bad ones?

Is it possible to erase all pleasant memories of a time in life while being able to recall all of the negative memories from the same time?

What do you think?