TOO much good luck no less than misery
May kill a man condemned to mortal pain,
If, lost to hope and chilled in every vein,
A sudden pardon comes to set him free.
Thus thy unwonted kindness shown to me
Amid the gloom where only sad thoughts reign,
With too much rapture bringing light again,
Threatens my life more than that agony.
Good news and bad may bear the self-same knife;
And death may follow both upon their flight;
For hearts that shrink or swell, alike will break.
Let then thy beauty, to preserve my life,
Temper the source of this supreme delight,
Lest joy so poignant slay a soul so weak.

Michelangelo Buonarroti

http://www.poemhunter.com/poem/joy-may-kill/