ETA: As a GM I've tried to turn a PC leaving into something beneficial for the campaign, if possible. If the player doesn't want me to use his character (never happened, ever) then I wouldn't use it. But, it can be a fun thing even while losing a party member and player. Dramatic death of a loved character? Set him up as a new resourceful NPC contact for the party? Or, the opposite. The Jedi Padawan has to leave the group? He tended to not get along with the other characters? He is SO turning to the dark side and returning as a nemesis.
![]()
Yeah, I was playing in a game where I realized I was really not enjoying the character and wanted to retire it and reroll. I was able to justify my departure in-setting by getting an NPC to assist the group, in return I would go work for him (which he had previously asked me to do, and made a generous offer, which I refused).
So in the end the group got the support it needed, my character left on very good terms, and I got to reroll to another character I have been enjoying more. Everyone won.