Stop being the person who sets themselves on fire to keep others warm. You should never have to become uncomfortable in order to make others comfortable. This is something I have fallen victim to too many times. I have been compromising myself for others since middle school.
I thought that in order for me to keep my friends then I needed to be and to do everything that they wanted. I became very unhappy and in the end, it never allowed me to keep my friends. So I became uncomfortable for the wrong people, but in all honesty, there is never the right person to become uncomfortable for.
I am now a freshman in college and sadly, it took me this long to figure out that the right people would never make you uncomfortable nor would they want you to be uncomfortable. Just know that you can make others happy without compromising yourself.
When you don't set boundaries to avoid upsetting people, just know that it does not make you a good person. When you sacrifice your needs in order to keep other people comfortable or happy, you are only hurting yourself. You should not have to sacrifice your needs in order to demonstrate your care for someone else.
Most importantly, people aren't going to know that they are hurting you in the first place if you allow them to believe what they did was okay. You have to learn to speak up for yourself when you're uncomfortable or unhappy, it is just part of growing up. If you allow people to overstep your boundaries consistently then you are going to become someone who is always drained, hurt, and eventually running on empty.
The right people would never want you to compromise your own happiness in order to keep them comfortable. Those people who do are selfish and probably don't care about you, to begin with. Your true friends may not always understand your boundaries, but they will respect them no matter what.
If you set a boundary and it upsets someone or makes them uncomfortable, so what? It doesn't mean you should remove the boundary, it means that you should remove that person. At the end of the day, your self-comfort is more important than other people's comfort.
Self-comfort or self-care is not selfish. Other people's comfort and self-care is important as well, but that does not mean you have to compromise yourself in order for them to have that. It is okay to want others to be happy, but do not ignore your own needs in order to give it to them.