I helped my ex when he was financially struggling. Now that I am in his position, he doesn't feel the need to pay me back what I let him borrow.

My ex owes me around $1k. He swore up and down that he would pay me back, as I was the only person who helped him during his rough times. Thankfully, he kept his word, as his original debt was $5k, but he is now going back on it, as I no longer want anything to do with him. He has told me that he does not plan on paying me back because "of how I am treating him". What would you do? I reached out to his family to see if they could talk some sense into him, but they don't care. I hate having to ask for MY money back, but I really do need it.