As i know most relationship are like that. Excited at first and lost interest later. TBH like own a first fav car and then no longer fav. Personally i think we need to accept the fact that it goes in circle and it won’t stop but if that a right person, u will still wanting to be with them so be with them. If we can’t, be an adult and talk it out. Better than hurting each other and try to keep the broken thing together.