I have been guilty of this as well and as I read letters and post some myself, there is a part of me that says to everyone who is yearning for the one the they let go/got away.
We are more than the person that we long for. We should stand tall, see that we are good people who just want our love returned / rekindled.
Firstly, if that person that you long for cannot see that, sadly it will be their loss because they are not ready for your greatness. Learn to love the person that you are. Leave them alone (as hard as that is, i know, i’m experiencing that now), let them miss you. Do not contact them. If they realise what their loss is, allow them to contact you and be open to the contact, but you must once again become someone that is worthy of a relationship. In your current state? Would you go out with you? Become the person that they fell in love with again.
Secondly, if it is a person that you love and you wish to let them know. Tell them! Really, don’t long for the right moment, it may be just what they need to hear, just let them know. If it isn’t what they want to know, feel unburdened by a simple message to them on a hand written note that you love them and you realise that they need their time. They may/may not come back, but you can release this weight you are carrying. If you died tomorrow, you would be always saying ‘what if.. ‘. Don’t guess, act!
My b/f has just broken up with me again (having to sort out issues). I will not contact him any further apart from a hand written note that I gave him the other day just saying, I was OK with us breaking up and I agree that we need time apart. This stops me sounding desperate and gives me time to get back to ME. If he comes back, he does so on his own accord and in the meantime, I can start to try and function again. I will leave it for a month before I initiate any contact, unless he contacts me first.
I hope that maybe this has helped if only 1 other person.