Being "in love" and "the fog" are one and the same--both are that stage of attraction and intimacy that has no basis in reality b/c there has not been enough time to learn enough about the other to know if they have a character worth your true love.
I'm pretty sure "the fog" is why they say, love is blind.
Remember: you fall in love with personality, but you have to live with someone's character. You only know if it is love if their character allows you to continue having that "in love" feeling, at least occasionally, after a few years together. Most of the time, discovering someone's character flaws will end that feeling and we move on--unless we've made the mistake of marrying before we discover that character. That's when things get really tricky.