For this reason, the Believer has no right to merely fear that their deeds are invalid, rather they are obliged to make their actions valid in accordance with the sound teachings of the Prophet (may Allah bless him and give him peace).
It is a good quality for the Believer to have a level of fear in regard to their deeds not being accepted. This fear stems from our belief that no matter what we do of righteous works, Allah Most High deserves greater than that. However, if this fear becomes excessive, it may lead one to despair.It is sufficient as a consolation that Allah Most High says, “Say, ˹O Prophet, that Allah says,˺ “O My servants who have exceeded the limits against their souls! Do not lose hope in Allah’s mercy, for Allah certainly forgives all sins. He is indeed the All-Forgiving, Most Merciful” [Qur’an; 39:53].
For this reason, it is important for the Believer to have both hope and fear. We hope that Allah, out of His Divine Mercy, accepts our deeds, however, we fear that our deeds were deficient and could have been performed better, with more presence of heart or more sincerity etc…
This brings us to one last point which is that the Believer must have a good opinion of Allah Most High.
Having a Good Opinion of Allah
The Messenger of Allah (may Allah bless him and give him peace) narrates that Allah Most High says, “I am according to My slave’s opinion of Me; So let them think of Me as they wish…” [Tabarani].
In another narration, Allah Most High says, “I am according to My slaves’ opinion of Me. If they think of Me in a good way, then they have it (i.e. good) and if they think of Me in a bad way, they have it (i.e. bad)” [Ahmad].
Remind yourself that Allah Most High wants you to succeed and He wants to show you His mercy. The fact that you are concerned about your faith shows that He has concern for you. Had He not cared about you, He would have made your concern about otherworldly things.
Strive to learn your faith, start with the basic foundation of knowledge regarding Islamic beliefs, Worships, and Spirituality, and strive to implement what you learn.
Whenever you slip, turn back to Allah Most High, ask for forgiveness, and return to striving.
May Allah grant you the success of this life and the next and bless you with that which only He can give.
Allah knows best