how come sometimes we meet someone and just fall head over heels for them even though there are prettier people out there

You're young, you've got things to learn. All of us, both men and women, are initially attracted to physical qualities we personally find attractive. But to hold that attraction there has to ultimately be underlying qualities we find near to our heart.

Now, what also happens is, we'll meet someone that doesn't initially thump or heart right off the bat. But as you get to know the person, they align so much with the person you are, that your attraction grows immensely towards them.

That's a keeper.