I wish I could even get that far.
But honestly, I get the impression that most happy successful people (and even many others) do that to some extent with selective memory and denial. Sometimes people mistake memories of dreams for memories of real events. I do think people's memories can be altered. That's why I was feeling hopeful about some kind of radical intervention.
I know it's not the same
@Lovequenel but one of the techniques I developed during my darkest days was a variant of the mnemonic memory strategy, the method of loci, that I call my "happy memory palace". Essentially, I have a mental map of a childhood family home which holds fond memories for me, and whenever I'm feeling sad or besieged by bad memories, I can step into that mental image and walk a set route through the house. Inside I have hundreds of places where I've placed different mental objects, each one is associated with a really happy or positive memory, and by walking through and focusing on a particular object, I can recall that particular happy memory and all of the lovely emotions attached to it.
It takes practice and rehearsal and I recognise that it's probably different for me seeing as I'm not clinically depressed, but it's an example of how I use a memory strategy as a coping mechanism. Another technique I've used often in the past is a memory destabilisation technique that I adapted from research into treatments for PTSD, it's similar in some ways to the process by which EMDR works.
As I think I discussed above, there will be a point in the future where TMS or other brain stimulation techniques might be used to erase specific memories, but as of yet, although memories are plastic and able to be manipulated to an extent, there's still no golden bullet.