I'm not sure I would qualify anything as a triumph or joy. It's not like I'm winning the Nobel Peace Prize. I sometimes use the therapist when I feel like bragging about something. I wouldn't do that with people irl because bragging isn't a good look on anyone. But if I'm feeling smug about succeeding at something, I might mention it to the therapist just to get the urge to gloat out of my system.

ETA: I am not an advocate of false modesty so much as I think talking about one's accomplishments is uninteresting to most others. There are certain situations where it might benefit the other person, but that isn't usual. For example, if my sister gets a raise, promotion, or some other recognition at work, I am interested in hearing about it. But I couldn't care less if an acquaintance gets those things. A therapist can be used when there is an urge to tell somebody without worrying about burdening them with the social expectation that they act excited/enthusiastic/etc.