The match ended with a win and we were both happy. Personally, I wasn't concerned about receiving any money from him as I was more focused on my recovery to not set a bet or deposit ever again. However, the next day my friend avoided me and didn't follow through on his promise even though I wouldn’t have minded if he didn’t.
To address the issue of how to talk to your friend without embarrassing them or making them feel pressured to pay, I suggest a direct but empathetic approach...
Invite your friend to a neutral and comfortable place for both of you, such as a park or a quiet cafe, or even a nice place you often go together where you can talk without interruptions. Make sure the place is conducive to open conversation, then express your happiness that they won and ask how they feel after this big win.
Also talk about your own journey of recovery from gambling addiction, explaining how you noticed the change in your mindset after winning and how it led you into a vicious cycle, but speak without judgment. Finally, instead of focusing on the promised money, offer your support in their journey of self-control, let them know that you understand the temptation and that you are there to help them by suggesting strategies you have used or money management techniques that can help them control their impulses.
Finally, suggest an amicable agreement where you both commit to supporting each other in times of temptation and agree before making any significant bets to discuss the risks and benefits, acting as a reality check for each other.
The most important thing, much more than the money, is always the friendship, and I'm sure that once that is reestablished he will feel obligated to fulfill his promise on his own.