What is forever?

Eventually all my past gets reduced to a snapshot. A snapshot somewhere in my mind. It does not necessarily have a past or a future. It's just there. The mind's way of compressing and archiving old times I guess.

I remember a 3 year old, sitting by the canal. The canal right in front of my house, trying to get his car collection to float on water. (No points for guessing who the 3yr old kid was). Apparently, the cars were metal and I saw nothing of them after that. But I don't remember that, people tell me about it but I don't remember it... only that scene, a 3 yr old by the canal, from the entire first 4 years of my life.

And there are more. The shrivelled old woman, what was her name.. amma? walking me to the skating rink. She was our maid. I was 7 then I think, but the picture is vivid, very vivid.

My grandfather and me holding his little finger (that was his way of holding hands). Is that all I remeber of him? Possibly.

The empty water tank on the top of the building, and three kids inside, feasting on the raw mangoes they had just plucked(I think stolen is a better word) of the tree. How old was I then, 10?

The not quite so little kid, peering through the telescope. His first sight of the orion nebula.

There are no photographs that capture these moments. They probably aren't even true. I cannot have seen these things. They are in the third person! Its like the mind moved aside and captured the scene. The scenes in themselves probably happened though.

The thing is these moments are generic. They are just everyday things. So how does the mind choose which of these to preserve. Is it completely random? Or is there some design?

Which moments of my life now will stay with me.. forever? And which won't?