Wistfulness, the menace of the happy!

Why is it, that having found happiness and being perfectly content, we still look at the neighbor's grass and wish it could be ours, or think back to the time when it was.?!

This is what it's all about

When to the Sessions of Sweet Silent Thought

When to the sessions of sweet silent thought
I summon up remembrance of things past,
I sigh the lack of many a thing I sought,
And with old woes new wail my dear times' waste:
Then can I drown an eye, unus'd to flow,
For precious friends hid in death's dateless night,
And weep afresh love's long since cancell'd woe,
And moan the expense of many a vanish'd sight:
Then can I grieve at grievances foregone,
And heavily from woe to woe tell o'er
The sad account of fore-bemoaned moan,
Which I new pay as if not paid before.
But if the while I think on thee, dear friend,
All losses are restor'd and sorrows end.

William Shakespeare