No kind of relationship can be all one-way. It simply doesn't work. There always has to be give and take, in any kind of relationship. If you find that you're giving and giving and not getting anything in return, it may be time to let that relationship go.
I would like to add a thought to that, approaching it from a slightly different angle.
Do people who could give something back actually realize that they should perhaps give something back? If someone always comes across as "strong" or "heroic" it is easy to think of them as not requiring the appreciation, or perhaps even help, they might sometimes want or need. After all, isn't giving without wanting something in return, doing things just because they are the right thing to do, part of how most people would define a "hero"?
It can be easy to forget that you shouldn't just take, but also give something back, when selflessness is what people see as your prime motivation. They might even believe that you are happy with just the knowledge that you have done a good thing and that that is the end of the matter for you.
Now, I am not saying that you should "bill" people for what you do for them in a figurative, emotional sense, but how certain are you that the people you expect something from actually understand how much it would mean to you if you received something in return? Are you at least strongly hinting at your own needs now and then, or do you expect them to be telepaths and know what you need and when you need them? (The latter is a bit of a drastic way of putting it, I admit, but exaggeration can help make a point.)