I think when you’re transitioning from being a people pleaser into someone with more boundaries it can feel so weird & it's hard to tell if you’re being mean or if you’re actually just respecting your own feelings, because you’re so used to putting other people's feelings first
It's a very uncomfortable feeling since to say it somehow our happiness is the happiness of others. When we touch ground and have burned ourselves until we can't function anymore though, and decide to look for ourselves, it almost feels alien, we feel somewhat guilty and egoist.
The truth though, it's self respect and putting priorities and boundaries.
It will get better with time, it won't get easier though.
I don't even know how to respectfully phrase the boundaries. I will sound rude anyway, right? :/
In a sense, it's not what you say but how you say it.
If you've transmitted the message respectfully, which is your right to make yourself a priority and people don't take it well, then it's not your problem anymore.
It's not your work nor your job to take responsibility for the 'unhappiness' of other people.
If people don't accept you setting rightful boundaries, then respect yourself and walk away. It's not worth the effort to argue with such people.