Who wins the battle of head vs heart?

"Oh, why'd ya have to be so cute?
It's impossible to ignore you,
Must you make me laugh so much?
It's bad enough we get along so well"
- "Goodnight and Go"
Imogen Heap

At times I can be logical. I let my head rule my actions, rather than my less logical emotions. This is when I trust my perspective.
Last night, I almost felt logical. One simple thing that he said lent clarity to the situation. The funny part is that our situation is really more black and white than I wanted to view it as. It seemed easier to view it as shades of gray. Doing so gave me more leeway and excuses for our actions.
Why is it when you really like a person, it becomes easier to make excuses for things that don't normally make sense?