How to know what can't be known in times of love and war

There are two basic mechanisms that we mere mortals use to assess a relationship, our hearts and our minds. One is tangible, the heart, and one is intangible, the mind. Mind you, we don't actually make choices with our heart, the beating organ inside our chests. Rather, we make some choices with our instinct, which we've traditionally said it's the heart. "Follow your heart," they say. "Do what your heart tells you," others claim. On the other hand, our minds are all about reason and thinking things though. "Think before you act," the ancients counseled. "Give it a second thought," my parents said.
So which one do you follow? And which one is right?
The trick to this dilemma is that neither is right. Both ways of thinking about relationships and/or other issues are valid. Some of us use one instead of the other. Others use both. Many use none.
It's funny, in both instances, when we like or dislike someone, we tend to use the heart more than the mind. We hardly ever stop to think about why we feel the way we do. We just do. We see our worst enemy and right away go into self-defense mode. We don't think about why we're reacting that way or why they are acting the way they do. We just react, from the gut, with our hearts. Likewise, when we see someone we like, we chase them against all consequence, not really worried about tomorrow.
But the heart can only take us so far. After a while, the mind manages to break through the barrier and help us see things clearly, more objectively. But this process usually takes time. For example, in those who are abused by their partners, their heart might not give into their mind for a while. These are the people that just won't leave because their hearts tell them not to.
I believe we would be just a little better off if we could think and reason through situations before going with our hearts. This is way more easier said than done, however. What is the first thing you do when you're confronted by someone you like. You certainly don't think about his or her income or whether or not he or she will make a good partner. No. You just want to jump their bones and ask questions later. It's natural. But we would be better off if we thought things through just a little bit before falling in love or getting in a fight.
Then again, the future is always in motion, hard to see. So we say, "what the hell", and we jump in with both feet. Because there is no time like today to do things, to fall in love, or to hate someone. You don't want strong emotions to be lost in seas of reason because, who knows, you might miss out on something very exciting.