Occasionally a person faces various physical and spiritual sorrows and troubles in the world. Amongst these are feelings so intense that they cannot be compared with any other physical pain. This feeling that causes such great distress in the human soul is a feeling called "regret."
There are two completely different forms of regret, however. The regret felt by people of faith and the regret that non-believers experience. These two feelings are extremely different from one another.
Believers are the people who have an absolute faith in the fact that events take place by Allah’s Will, and whatever befalls them does so by Allah’s Will. This explains their all-important distinctive attribute of putting their unyielding trust in Allah, at good times, in trouble or when they make a mistake. The Prophet Muhammad (saas) pointed out the strong character of the believer with a comparison in the hadith below:
The similitude of a believer is that of a standing crop in a field which is shaken by wind and then it comes to its original position but it stands at its roots. (Muslim)
Upon making a mistake, a believer immediately repents with sincerity and hopes for Allah’s forgiveness. As a result, he does not suffer from a distressful and long-lived feeling of regret. The regret felt by believers urges them to ask for repentance, to purify themselves and prevents them from repeating this error. It helps them rectify their errors and prevents them from plunging into a distressful and pessimistic mood. Moreover, this regret does not reduce their enthusiasm, devotion, or religious zeal nor does it drag them downward into a spiral of apprehension and depression.
Regret felt by disbelievers, on the other hand, is very distressing and long-lasting, as they do not put their trust in Allah when they encounter a difficulty or commit a transgression. Throughout their lives, they often use phrases like "I wish I had not done this…" "I wish I had never said this…," and so on.
*a masterpiece by harun yahya*
aite...no hal! 
meaningful…=)
pas de regret2 eh.. hehe..