When you think someone is upset with you, you begin to people-please, compliment, and try harder for their approval
Though it can be difficult to remember in the moment, when someone behaves badly, it's up to them, and not you, to fix the situation. Modifying your behaviour to accommodate theirs only sets an unhealthy precedent and makes you being the one to compromise the norm.
You have a history of being 'nice' to avoid harm, and this has become a survival skill
Nobody wants to deal with conflict when they don't have to, but if you find yourself bending over backwards to keep the peace, you'll likely be dealing with a lot of emotional burden. Freeing yourself from the expectations of others is both liberating and good for your mental health.
You tell people 'it's OK' and comfort them after they hurt you, even though it really isn't
Expressing how you truly feel, especially in a tense situation, isn't always easy. But if you find yourself excusing bad behaviour and being unable to speak your mind, it might be a sign that you're being taken for granted, and need to set clearer guidelines of the honesty and mutual respect you expect from the relationship.
You fear being labelled as 'selfish,' 'toxic', or 'not empathetic' for having reactions that are 'not nice'
Of course, we always want to be seen in the best light possible. However, we shouldn't let the fear of being considered a 'bad friend' stop us from responding to other people's toxic behaviour. You should feel able to discuss your feelings - good or bad - in a calm and reasoned way with everyone in your life, without fearing the reaction.