you don't, you have to stand back up and walk away, real love is forever, if you ever stop loving someone, you never really loved them at all, that doesn't mean you can't move away and find someone new to love though
You just do. If your "inner personality" is getting what it needs from a relationship, it loses interest in the relationship and stops producing the above-mentioned dopamine. And then your "conscious mind" loses interest. Bing; it's over!
Numerous factors. The easiest to understand is growth. Quite often 1 grows mentally and spiritually faster than the other, or they just grow apart. Needs change, things that you thought were important all of a sudden don't mean a thing. The other side of the coin is STUPID human tricks; cheating, lies, not realizing nor appreciating what you have, If the honesty & trust are gone, so is the love, you just can't have the realationship you've always wanted. You can forgive, but you'll never forget. When there's doubt, it's time to go
I think it would take something horrible to happen for you to fall out of love. Now, if you no longer want to be with this person, break up. And with breaking up you're still going to have to deal with your feelings.....Bottom line it won't be easy.