Don't be sad : live today as if it were the last day of your life. With this frame of mind and outlook towards life, you have no reason to allow sadness or anger to steal the little time you have...Being preoccupied with the past and dragging past woes into the present - these are the signs of an unstable and unsound mind"
Sumber : Don't be sad, by Dr Aaidh ibn Abdullah al-Qarni