stop wishing for things that will never happen

I wish for many things. Things that probably will never happen. I have a really good boyfriend, but I keep wishing myself back to last year when I loved someone else. I keep wishing for him to be the one. With him I felt love, but it was also horrible when it broke, and I was left with nothing. And now I've got everything to lose, and I'm still considering sacrificing it for something that is so uncertain. I don't know what to do. I feel lost. If you always search for something more, will it leave you with even less?