What do we celebrate on Eid?

On the day of Eid-ul-Fitr, Hazrat Ali (A.S.) delivered a sermon in which he said:

"O people! Verily this day of yours is the day when the righteous are awarded and the wretched are losers. It is a day which is similar to the one on which you shall be standing (before your Lord). Therefore, when you come out of your homes to go to places of your prayer, remind yourselves about the day when you (your souls) shall come out of your bodies to go to your Lord. When you stand on places of your prayer, remind yourselves of your standing in presence of your Lord (on the day of Judgement). And when you return to your homes (after prayer), remind yourselves about your returning to your homes in Paradise." (Nahjul-Balaghah)

Eid is not a celebration about an end to fasting and prayers, but a celebration of gratitude around the spiritual renewal and purification that we had the opportunity to be granted during the month.

Did we get nearer to God? Did we remove a bad habit? Did we find joy in Qur'an? Did we abstain from a temptation? Did we acquire humility and patience? Did we enjoy secret conversations with our Maker? Did we increase taqwa and will-power? Did we, perhaps, find forgiveness? Did we open our hearts with charity? If we experienced any of these, there is the cause of celebration. Eid can be a day of great loss if we let the month pass without improving ourselves and without turning to our God. It can be the end of wasted fasting if we return back from any gain of the month to former bad habits and celebrate the relaxing of our hearts to vanity, waste and sin.

What do we celebrate on Eid?