1. The piety and humility of the Salaf
When Ramadaan came to a close, the rightly guided predecessors (As-Salaf As-Saalih) used to frequently seek forgiveness, repent to Allaah – The Mighty and Majestic – and fear that their (deeds) would not be accepted. They used to exert themselves (in worship) in Ramadaan and outside of Ramadaan, afterwards they would be fearful that none of this will be accepted.
2. How the Salaf behaved when Ramadaan was approaching and when it left
They used to seek the forgiveness of Allaah and repent. So much so that it was reported that they would supplicate to Allaah for six months that He would allow them to reach Ramadaan. If He allowed them to reach Ramadaan, they would fast, pray at night and supplicate for the next six months that He accepts the month of Ramadaan from them.
3. Signs that Ramadaan has been accepted
Following good deeds with good is a sign that (an act) has been accepted, whether it is pertaining to Ramadaan or other than it. If the Muslim is in a good state after Ramadaan, performing many good deeds and righteous actions, then this is a proof of acceptance.
4. Signs that Ramadaan hasn't been accepted
If the opposite is true, and he follows good with evil, and as soon as Ramadaan is over he follows on from this with sins, heedlessness and turning away from the obedience of Allaah, then this is a proof that it hasn't been accepted.
Every person knows their true situation after Ramadaan. So let them look, if they are in a better state, then let them thank Allaah, as this shows (that it has been) accepted.
If their state is worse, then let them repent to Allaah and seek the forgiveness of Allaah, as this is a proof that it hasn't been accepted and it is a proof of negligence and carelessness.
5. Do not despair of the Mercy of Allaah
But the slave should not lose hope of the mercy of Allaah. He should not close the door that is between him and Allaah and despair of the mercy of Allaah.
"Say: O my slaves who have transgressed against themselves (by committing evil deeds and sins). Do not despair of the Mercy of Allaah: verily Allaah forgives all sins. He is Oft-Forgiving, Most Merciful." (Az-Zumar: 53)
It is upon him to repent, seek the forgiveness of Allaah and return to Allaah – The Mighty and Majestic.
Allaah – The Mighty and Majestic – accepts repentance from those that repent.
"And He it is Who accepts repentance from His slaves, and forgives sins, and He knows what you do." (Ash-Shura:25)
And the peace and blessings be upon our Prophet Muhammad.
By the Shaykh, 'Allaamah Saalih Al-Fawzaan
Ithaaf Ahlil Eemaan bi Duroos Shahr Ar-Ramadaan pg. 119-120
~*Syed Ibrahim (Talha)~*