Go-to guy

When you’re the “go-to guy” meaning you’re always there/ dependable….where does the “go-to guy” go?  I feel like I am the go-to guy for SO many….but I don’t have anyone to go to and lately all these requests are so exhausting and I’m being stretched in so many directions that I’m losing me in the mix…but I can’t say no….if I say no…others would be left stranded and in some instances it’s life or death.  What happens to someone that makes them the “go-to” and others the “don’t go to”?  I was listening to a recent discussion between colleagues about a similar topic and they simply said you just need to set boundaries … but that doesn’t work.  Am I supposed to tell the family member I can’t take them to chemo, or the ER, or to their scan?  Am I supposed to tell me child I can’t play because I’m so damn tired?  Am I supposed to tell my job no but if I do others will suffer?  I get setting boundaries but what if you literally can’t set those boundaries because it could cost others their life?