need help with my best friend

i want to change the dynamic between my best friend and i. i wanna make it clear that i do love them dearly and don’t want to make myself unavailable to them. however, we’re carrying on the same dynamic of friendship that we had in hs and i think it’s time for a change. when we were in school, it was fun and okay to be so involved in so many aspects of each other’s lives. it was okay to be involved in each other’s relationships and mental health and parent issues. but we’re not in hs anymore. we both have adult problems and handle them in the best ways we know how. i don’t want to be involved in their adult personal business. i don’t want to be involved in every aspect of their life anymore. also here recently i feel that they’ve been dumping all of their problems on me. last summer i did the same thing (without realizing ofc) and their response was that they needed a break. that really hurt me, but it feels like it’s okay for them to act how they want but when i have an issue it’s okay for them to bail. i don’t know how to set these boundaries and i’m scared it’s really gonna hurt my friend. also after one of my friends committed suicide last summer, i feel morally obligated to be everyone’s emotional support person. i don’t have the resources or the mental capacity to be that person anymore while i’m healing from my own pain. how do i set boundaries in a clear, but respectful and healthy way??