Quit gambling? I never heard someone that quit on gambling after making tons of profit because most of them still play but in moderated basis to still enjoy gambling and have fun with other players. Other successful gamblers choose the mentor path which they offer classes in exchange for their fee.
I think this is the only way for a successful gambler to quit by finding different steady source of income using their gambling knowledge.
I don't really know anybody that keeps making a profit while gambling lol. The best way to make some money out of gambling is becoming a streamer; look at all those popular gambling streamers on Twitch/Youtube such as Foss or Xposed. They get sponsored by the casino, still have fun and get a nice income out of it.