Tekashi 69 has pleaded with a judge for a reduced sentence, in a letter that says he feels as though his world is "crashing down".
The rapper, whose real name is Daniel Hernandez, is due to be sentenced on 18 December for gang-related crimes, Vulture reports, and is becoming "more and more overwhelmed with emotions".
His lawyers are arguing that he should be sentenced to time served because of his cooperation with prosecutors against his former Nine Trey Bloods associates.
"There is no excuse, no justification and no apology good enough in this world to explain my crimes," Hernandez wrote. "While I have been incarcerated, I have had time to reflect on the recklessness and foolishness of my decisions. I wake up every morning asking myself, 'Was it worth it?'"
The letter was read to the court a week after Manhattan federal prosecutors advocated for a reduced sentence due to his "incredibly significant and extremely useful" testimony against members of the Nine Trey Bloods.
"Despite the significant threat to his music career and his personal safety, Mr Hernandez, a very well-known public figure, publicly testified both credibly and powerfully in a highly-publicised trial, which led to the convictions of two Nine Trey members," his lawyers wrote.
"Considering his significant cooperation and assistance, there is simply nothing else that he could have done to further his cooperation. He did everything asked of him, and at times even more."
His lawyers added that Hernandez had shown "courage and integrity" by testifying despite the "significant safety risks" involved in such a trial.
Hernandez pleaded guilty to nine federal counts after being arrested for racketeering. After making a plea deal, he agreed to cooperate in giving evidence against members of the Nine Trey gang, in return for a more lenient sentence.
He is facing 47 years to life behind bars.