I listen to some of my clients tell me how hard they try to "do things" or "make time" for a "certain someone," but that someone isn't putting in a similar effort. Okay, I get it, you're disappointed, but you're hopeful; you think that person will somehow change over because you're forcing them to do so? If this is the case, you may be missing one of life's important lessons: Nothing true can ever exist (or last) if it is done by force or by placing your agenda-filled ego as the main driver.
I know all relationship/friendship circumstances can be very different, and so the best solution for each can vary. BUT here is the essence that would be wise to bare in mind — and that is... if someone really wants to be a part of your life, they will really make an effort to be in it. There's no need for you to try so hard.
At some point, we all make this "mistake" of trying too hard to change someone over. The truth is... it's okay to make this mistake once or twice so you can learn from it. After all, how can you learn from a place of comfort and convenience? HOWEVER, what's not okay is if after a few rounds of this kind of drama you still don't learn from it; you continue this habit of choice over and over again only to complain or feel angry about it.
You do not have to settle for being somebody's part-time, or somebody's some-of-the-time, or even somebody's when-they-have-time. You deserve somebody who can be there for you all the time; whether in person, in mind or at heart.
You do not have to settle for anything that compromises your inner balance unless you choose to. Communicating truthfully and kindly to yourself and the other person is always KEY. Again, the choice is always yours to make. Ask yourself "What kind of choices do I truly want to experience in this lifetime?"
Yes, I know it's a tough choice to make especially if you're emotionally invested, but just keep in mind that when you stop chasing the wrong things, you will give the right things a chance to catch you.