Falling in love is not an illusion, as much as falling out of love is a fall from grace. What we see when we fall in love is not illusion but truth. We want to fall in love because we want so much to return to God. Of course we want to escape a darkened world. We want desperately to go home to a place where all of us can see how beautiful we are.
Some people say that falling in love is a state of denial.
It is, actually. Guilt is the ego's orgasm. Most people do not have the personality structure to hold on to the strength it takes to love without judgement. And so love's magic dies, casting Adam and Eve out of Paradise. As our minds are illumined, we become better at romance because we become better at being human.