How do I avoid falling out with people I depend on without being exploited?

I feel like if I'm not assertive towards people I depend on for my living situation, whether it be family, my boss or landlord, they just exploit me.

However, I can never seem to do this without having a heated exchange about all the ways they've used or taken advantage of me, so I'm often compliant to begin with to avoid conflict.

The problem is, they then take advantage of my compliance, where it gets to this breaking point where I end up burning bridges with them. I then become extremely regretful about actions I should or shouldn't have done and the cycle repeats.

If my living situation changes because I fell out with a landlord about some aspect I'm not happy about, I'm now super careful about saying something that might upset my boss. So my boss then exploits me and now I'm regretful I didn't say "No, I won't do that."

It's not always easy to find a new job or new place to stay so I feel like I'm at their mercy but I also can't show weakness or they'll just walk over me which seems to happen a lot until I tell them to their face what I really think about what they're doing.