Saying yes to everything that someone asks from you can land you in so much trouble! Too many YESSES can burn you out because you might overload yourself, and in the end, you are the one suffering.
People get so used to the fact that you are willing to help them because you always say yes, that they start to take advantage of your good nature.
Just because you are willing to help doesn't make you anyone's slave.
Just because you are willing, doesn't mean you should just say yes to everything!
To say NO is not selfish, or evil!
As humans, we tend to help others because it is in our nature. To say NO sometimes takes a lot of courage because we don't want to disappoint others, but maybe for once, you have to think of yourself rather than about others.
Even though we give our lives to our families and work, and we give up a lot to be able to provide for them, we do need time for ourselves. You need time away from work and sometimes family, and it is YOUR responsibility to create time for yourself. If you burn yourself out then you are not useful to anyone.
In Matthew 5: 13 God says:
“You are the salt of the earth, but if salt has lost its taste, how shall its saltiness be restored? It is no longer good for anything except to be thrown out and trampled under people's feet."
You always need to be true to yourself and know your limits. You need to know that YOU are also important.
Learning to say NO might not be the easiest thing on Earth. We might be scared that we hurt someone's feelings, but often enough the other person might just accept the no and move on. It might not even be such a big deal, and we beat ourselves up over something that is not really worth it.
In Matthew 5: 37 God says:
"Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from evil."
This obviously doesn't mean that you should just say NO to literally everything that is asked from you, but if whatever is asked puts too much strain on you, then you should make up your mind fairly quickly and just say NO.
You don't even have to explain to anyone why you say NO. Put a smile on your face, listen to the request, and then with a smile on your face, just say NO.