That falling out of love concept is really my big fear.
Don't overthink it. If you are aware that this could happen, you will be able to see it at its earliest ;)
Did you communicate about it with your partner? That's probably a great starting point. Go for a chill afternoon of opening. Sometimes, we go through so much together that we take the other for granted, or just forget to open-up and share our innermost feelings with enough room of both space and time.
Gif us an animated picture!