Ask yourself this, are you kind? or are you actually a helpless person who can't say no?

I am not being mean, this is an important question to ask yourself. A kind person performs acts of service out of their own goodwill for the benefit of others. However, the other helps others because they feel the need to be socially accepted / etc. It is similar in your typical movies/shows in which a nerd helps the popular kid in his school work.

If you indeed help others because you truly want to. Remember this. You should always keep this acts of service sustainable and mentally/physically healthy for you. If all you have to do is sacrifice part of your time to make someone's day better, go ahead! Well, research has shown by helping others, it leads to the production of oxytocin. That is well you feel great after truly helping someone. However, if it leads to sacrificing something important to you, like your grades or material possession, you should think it through before helping that person.