True Believer

Muslim and Momin
Allah distinguishes "Muslim" from "Momin" [33:35, 66:5]. The one who believes in the Divine Law, is a believer [i.e. a Momin]. The one who conceals or rejects the Divine Law, is a non-believer or KAAFIR. The one who submits himself to the Divine Law and lives according to it, is a Muslim. The one who violates the Divine Laws is a Mujrim, or arrogant or deviator from the right path.
Just being a Momin is not enough. Allah Wants us to be Momin as well as Muslim i.e. a Believer in the Divine Laws as well as a Submitter to these Laws. According to 43:69, those who will qualify to enter Paradise will be Momins as well as Muslims i.e. they will not only believe in the Divine Laws but also abide by these Laws. According to 49:14, one is not qualified to consider himself Momin until he is a true believer from the heart even if he submits or surrender himself to the Laws of Allah.

Ibrahim ibn Adham (ra) giving advice against disobedience
A man came to Ibrahim ibn Adham, may Allah be pleased with him, and said, "Abu Ishaq, I am unable to control myself. Please give me something to help me with it"

"If you accept five conditions," said Ibrahim, "and are able to put them into practice, your disobedience will not cause you any problem."

"Just tell me what they are, Abu Ishaq!" the man said. "The first is that when you want to disobey Allah you do not eat anything He provides." "Then how will I get anything to eat? Everything on the earth is from Him!" "So is it right to eat His provision and disobey Him at the same time?" replied Ibrahim.

"No, it is not. What is the second condition?" "When you want to disobey him, move off His land."

"That is even more difficult! Exclaimed the man. "In that case where will I live?"

"Is it right to eat his provision and live on His land and then to disobey Him?" asked Ibrahim. "No, it is not."

"What is the third condition?" "When you want to disobey Him in spite of eating His provision and living on His land, find a place where He will not see you and disobey Him there."

"What do you mean, Ibrahim? He knows everything that happens even in the most hidden places!" "So is it right to disobey Him when you eat His provision and live on His land and when you know that He can see everything you do?" "It certainly is not!" the man replied.

"Tell me the fourth condition." "That when the Angel of Death arrives to take your soul, you say to him, 'Give me a reprieve so that I can repent and act righteously for Allah.'"

"But he won't listen to me!" "Then if you cannot ward off death long enough to give yourself time to repent, and you know that when it comes there will be no reprieve, how can you hope to be saved?"

"What is the fifth?" "That when the angels of the Fire come to you to take you to the Fire, you do not go with them." "They will take me whether I like it or not!" exclaimed the man.
"So how can you hope to be saved?"

"Enough, enough, Ibrahim! I ask Allah's forgiveness and I turn to Him!"
The man's repentance was sincere and from that time on he was assiduous in his worship and avoided acts of disobedience until the day he died