You have get same effort you put in. No one enjoys being the friend who “does to much”. Or the friend who never gets anything In return. Yes you should be there for you friend as much as you can if you really care about them. However if this “friend” is only existent in your life, when something in their life has gone wrong. They aren’t really a friend. If this person is never there for you, blows you off, and simple treats you like crap. Speak up. You need to be straight up with some people, for them to realize what they are doing wrong. Yes you might feel bad about it at first, but remember you come first. You don’t need fake friends who are only going to use you. You have your own stresses already, and you don’t need “friends” who make life more stressful for you. 

If you put so much effort in, you are going to expect the same effort back, and be let down if they effort isn’t returned. As weird as it sounds, putting in to much effort can ruin a friendship. If you go above and beyond, to be there for your friends. And they don’t even cross the street in the effort scale. Eventually you won’t want to be your friend. You will get tired of being disappointed, and ultimately, the friendship/relationship will come to a end. 

So be there for your friends, but don’t put yourself into a situation, where the friendship could spiral into a terrible situation. Put in as much effort as you get back. Cut lose “friends” who only treat you wrongly, or are never there for you. You control who is a major part of your life, and who effects it the most. Chose wisely.