Rambles on Being a Friend

On Sunday our pastor continued thru Eccles. and he said something that I never really thought about. No where in the Bible does it talk about others coming to you, encouraging you, being your friend. It only refers to what you are supposed to do towards others.
This statement was timely. There are times when I have to say I seriously doubt some of the relationships I have with others and question if the friendship goes both ways. Times when friendships can feel more an opportunity of convience rather than a deepening and exhorting of one another.
I am learning that it is not how often others speak to you, but rather how often you speak to them. Some people just don't think about showing the initiative with all of those they know. I am probably guilty of the same...and don't even realize it - For that I am sorry.
It gets so frustrating trying to hold on to some of the old. Those who don't reciprocate in any way. Those who you run into and everything feels a bit awkward since you haven't spent any time with them. And then there are those who you can miss for ages and meeting up again is like no time has passed at all. Those souls that are knit like Jonathan & David. There are so many that I appreciate! love! They have been so faithful and have taught me so much.
I know that I need to stay faithful to do what scripture tells me, and yet my question is: at what point do you stop pursuing a relationship that obviously has no personal motivation or genuine desire to reciprocate? I know that relationships change with time and yet why do some appear so flakey. I'm tired of trying to continue those relationships. I will still be kind - I won't shun them. But I know that there are others who do share a desire to see and spend time with us. Those are the true ones, the faithful ones, the ones who seek friends themselves, the ones who don't forget the old when a new one comes along. Yes, the common bond of Christ should be what holds friendships together, but in a fallen world with shallow people (myself included) we seek people who share our interests or (very selfishly) give us something - be it items, praise, notice. We are called to just be a friend. To love those around us and show the fruit of the spirit with all men. Why does that come so easy with some and yet harder than rocks with others? Do you persue those people who don't sharpen you and make you stronger? Yes, all men are at different levels in their walk. At what point if a friendship changes to one of just usery do you step back from that relationship? Do you step back?
All questions that probably have answers. Ones I'm going to seek. I don't want to be hasty in this but part of me is hurt when it happens and is that selfishness? Is it just that I'm not getting my way? How do I know when the emotions felt are wise to listen to or should be ignored. I appreciated what our pastor said "To look forward to meeting new strangers who may be hidden friends." to bring alongside the faithful old ones - those who want to sharpen iron together.