Assalamulaikum for one big reason I promised to Allah I will never want Jannah,if my reason is stay or gone I realised that I did very wrong ,when I pray I don't want Jan nah, I want to repent what can I do plz kindly advise me.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Saying that you do not ever want Jannah is an awful thing to say. A Muslim should combine between fear (of Allah) and hope (in His Mercy). He should be keen on winning Jannah and should hasten towards it; Allah Says (what means): {And hasten to forgiveness from your Lord and a garden [i.e. Paradise] as wide as the heavens and earth, prepared for the righteous.} [Quran 3:133]

You must repent to Allah the Almighty and regret what you had said and be determined never to say it again, as repentance wipes out what the sins before it. Additionally, you should abundantly ask Allah to admit you into Jannah and seek refuge in Him from the Fire.

Allah knows best.