Sometimes games will allow you to mute yourself. This will be a setting within the games menu itself. This is a handy way to do what you want but obviously, it wont apply to all games and some games do not support this feature. I'm not sure if this can be done in the division 2 for example.
I don't think the PS4 will allow you to do this on a global level with a specific override setting but there is a way to do it. Simply create a new party and set it to private. Set the system to prioritise party chat. This way when you talk, the voice will go to the party and not the game. Since you are in an empty party, nobody will hear you talking. There may be a better way to do it but this doesn't take much work to do and does exactly what you want.