It's never easy to let someone go. It never will be, but sometimes, that's the best thing for you to do. Life will get easier, you do not need to wait for that person to come back anymore. They have moved on, you should too. It is hard at first to let that special someone go, but it is whats best. If they were coming back, they probably would have by now. You never know when that day will come when you do have to let go, but it will.
You may think that you will never be able to let them go, but trust me you can. It is definitely one of the hardest things you will ever have to go through. Also, one of the best things that you will ever do. You might wanna wait for them your entire life, but why waste your life on someone that isn't worried about you? Your life is more valuable than that, do not waste it on someone like that. They do not deserve your time.
You can meet someone amazing, maybe even "the one", but you wouldn't know because you were waiting for someone that was never coming back. You can really miss out on someone or something that is very special. Letting go was definitely one of the best things I could have ever done. It could totally be the best things you could ever do, but you have to do it first. Like I said, it will not be easy, but it will be better for you. Trust me.