Do you have sex with people you like when you are lasting a long time? Perhaps you subconsciously don’t like your self and so are in a hurry to get done.
Lighten up a bit: put on some music that you know you like, light some candles, relax and don’t rush your self so much.
Either that or go the other way:
You are a pathetic fat slob and have no business having sex with your self! Slap your self around a bit and go sit in a corner of the garbage next to the garbage can facing the wall whilst you wank. Call your self horrible names while you remind your self of all the failures you have had in life going back to early child hood. When you feel your self about to shoot a load slap your dick into the floor or wall and say, “You pathetic fuck! did I give you permission to come? I don’t think so!” When you do eventually pop it aim for your mouth or eyes and don’t wash up till the next morning.