Why is love so complicated?

I take time, patience, and kindness,
agreement, laughter, and tears.
For happiness to last, forgiving hears are needed.
I flow through every thought in your brain,
I make your heart beat faster and your blood pressure higher.

I am as old as can be,
I am every girls dream,
The boys are quite giddy when they get around me.
I can conquer anything,
and if it's true I'll last forever and ever!!!

What am I?!