Get yourself hard, look her in the eye and say out loud "Please forgive me for being such a loser (ex's name), I wasn't good enough for you". Say it 6 times whilst you stroke.
Now say "I am a pathetic stroker and I didn't deserve you (ex's name), I am not even worthy to look at you" Say it 6 times.
Keep stroking and don't you DARE cum.
Now you need to apologize for having such a tiny dick. After all, this was one of the reasons you split up.
So say, "I am sorry (ex's name) for having such a small penis and not being able to satisfy you sexually." Say it 6 times.
Get yourself to an edge.
Now get a photo of her current boyfriend or one of a stiff dick and continue.