It is good to be selfless but it does not mean one has to be people-pleaser.
Personal happiness is not defined by other people but by our respective needs.
Many of us want to be approved and accepted in our social circles hence we try to do almost anything just to get the nod of those people whom we seek to please. Selflessness is a virtue only if the giver does not get abused nor used.
Oftentimes, you go out of your way by not saying "no" to a friend even if "yes" means causing you a lot of disadvantage.
Learn to assert what is justly right for yourself too. Do not over bend just to accommodate other people.
What is important is that you are always fair and caring with others, meaning, you genuinely care about making other people happy and not becoming a reason for their problems.
Learn to love and respect yourself too. There is no harm in acknowledging what you rightfully deserve.