I met my boyfriend in 2015 when I was an au pair in Spain. We've been together almost three years now and only lived in the same country for about three months of that. We make it work because we are both dedicated to making it work. It takes patience, trust, and love. We spend a month together once or twice a year and we text/speak every day. Hopefully it won't be long until we can live in the same country again!
Perhaps if a long-distance relationship doesn't work, it's because it wasn't meant to work. I don't think it's something you can "believe in" or not... for some people it works, for others it doesn't, just like any relationship!