why one gets haunted with the past?

Leaving behind the childhood why we grow faster, why we leave all the glorious days when everyone is talking about us, everyone wanted to know you, wants to spend some time with you.

Those were the days when the whole world was revolving around you and you were busy in constructing your own world. while one day this all vanishes at once. when it vanishes doesn't know but it disappears like a cracker. you will not get any glimpse of those days, situations, minutes, seconds, hell lots of other tings. why this happens? donno know. wanted to catch those bitter sweet moments again.

In anyone's case, the bitter moments are the most joyous moments. may be the line is contradictory but it is true. will tell u how? these moments are those that are unexpected, unpredicted, unexplained but lasts for ever. why this happens may be a scientists headache but one can not erase them, wipe out them, eradicate them, eliminate them. We always say that these moments teach us a lot. I doubt. If they are teaching something then why do commit mistakes again and again. The answer is no. It may sound rubbish that the questions am i asking are all have negation but if some one thinks deep enough will get the answer or will not get.

Still, i myself ask this question why do we are haunted with bitter past or sweet past?

To conclude here is a beautiful poem by P. B. Shelley:

Time Long Past

Like the ghost of a dear friend dead
Is Time long past.
A tone which is now forever fled,
A hope which is now forever past,
A love so sweet it could not last,
Was Time long past.

There were sweet dreams in the night
Of Time long past:
And, was it sadness or delight,
Each day a shadow onward cast
Which made us wish it yet might last--
That Time long past.

There is regret, almost remorse,
For Time long past.
'Tis like a child's belovèd corse
A father watches, till at last
Beauty is like remembrance, cast
From Time long past.