You know what things trigger you and how you feel when you do certain activities. You know how certain people treat you and how you feel when you are around them.
People and situations that lower your self esteem are bad for your mental well being. Situations that trigger severe anxiety are bad for your mental health also. The same goes for things that you know will make you very sad or trigger depression.
We have to be proactive about our mental health and this means knowing ourselves. It means drawing boundaries with ourselves and with other people.
If we know that something is going to give us severe anxiety and we do not have to do it, then that is the time to stand by our no. If people want to argue then let them. We do not have to argue back. We can just tell them that we have made our decision and it is based on what it best for us.
Many people in our lives are more concerned about their own agenda than our mental health. They are not the ones that have to suffer the consequences of a decision that we knew ahead of time that we should have done differently.
Know yourself and protect yourself first. You can care about others and want to help them but you are better for them when your mental health is in good shape. People that care about you will respect what you do and do not want to do.