The only way love can last a lifetime is if it's unconditional. The truth is this: love is not determined by the one being loved but rather by the one choosing to love.
There is an old story from the Eastern tradition that says that when the gods created the universe, they found a place for everything but the truth, and this created a problem, because the gods did not want this wisdom discovered right away. One of the gods suggested the top of the highest mountain, another the farthest star, a third spoke up for the dark side of the moon, and another for the bottom of the deepest ocean. Finally, they decide to place truth inside the human heart. In that way, we would search for it all over the universe, with the secret within us all the time.
Love chooses to believe the best about people. It gives them the benefit of the doubt. It refuses to fill in the unknowns with negative assumptions. And when our worst hopes are proven to be true, love makes every effort to deal with them and move forward. As much as possible, love focuses on the positive.