One of the main differences between Prophet Adam a.s. and Iblis is their reaction after they’ve wronged themselves.
After Allah swt punished Iblis due to their refusal to prostrate to Adam, Iblis’ response was to put the blame on Allah swt, i.e. to claim that it is Allah swt the one that has led them astray.
“(Iblîs) said: “Because You have sent me astray, surely I will sit in wait against them (human beings) on Your Straight Path (16) Then I will come to them from before them and behind them, from their right and from their left, and You will not find most of them as thankful ones (i.e. they will not be dutiful to You)” (QS Al-A’raf 15-16)
In contrast, when Adam a.s. was sent down to Earth as a punishment, the first thing that he did was to admit that he made the mistake and then ask Allah for His forgiveness.
“They said: “Our Lord! We have wronged ourselves. If You forgive us not, and bestow not upon us Your Mercy, we shall certainly be of the losers.” (QS Al-A’raf: 23)
We clearly has made a lot of mistakes. Allah swt has put a feeling, i.e. the feeling of guilty, inside ourselves that we may admit those mistakes and then ask for forgiveness and mercy to Allah swt. This is the right way to react on that feeling of guilty; instead of feeling desperate and despair from Allah’s mercy.
After admitting that we’ve wronged ourselves, the next thing that we have to do is to do as much as good deed as possible. Prophet Musa (Moses) a.s., when he fled Egypt after killing someone, he was terrified and felt guilty; but watch what he has to say to Allah swt after helping two ladies taking water from a well:
“So he escaped from there, looking about in a state of fear. He said: “My Lord! Save me from the people who are Zâlimûn (polytheists and wrong-doers)!” (21) And when he went towards (the land of) Madyan (Midian) he said: “It may be that my Lord guides me to the Right Way.” (22) And when he arrived at the water of Madyan (Midian) he found there a group of men watering (their flocks), and besides them he found two women who were keeping back (their flocks). He said: “What is the matter with you?” They said: “We cannot water (our flocks) until the shepherds take (their flocks). And our father is a very old man.” (23) So he watered (their flocks) for them, then he turned back to shade, and said: “My Lord! truly, I am in need of whatever good that You bestow on me!” (QS Al-Qasas: 21-24)
In short, Prophet Musa a.s. said to Allah swt that he is in a need of any good deeds that he can do to compensate the mistake that he did. This is a very inspirational example on how we should react towards mistakes that we made; we should admit to Allah swt that we made the mistake, ask for His forgiveness and mercy, and then actively seek any good deeds opportunity. Indeed, “the good deeds remove the evil deeds (i.e. small sins)” (QS 11:114). May we always be on the straight path until we see our Lord in the hereafter.