why do people cant use their minds when they are in love??

Emotions can be very tricky, they don't think. That's why a lot of people makes a wrong decisions. Their decisions are based solely on their feelings. When we're in love our own concern is what we feel. We don't look consider our minds' thoughts.

This is what I observe people who are madly in love no matter what you says or wrong about her/his choice of partner she or he would defend her loved, even though you already says all the bad things about her sweetheart. many people who are in love act like blind, deaf and mute and even this person done wrong with her, he still understand to the point that he seem like stupid and never know anymore the right or wrong. here is an excerpts from a studies which explain why people act like dumb when in love;

Almost immediately thereafter, it is uncontroversial that when someone experiences an attraction for someone else, their brain triggers the release of certain chemicals. These adrenaline-like chemicals include phenylethylamine (PEA) which speeds up the flow of information between nerve cells, dopamine, and norepinephrine (both of which are similar to amphetamines). Dopamine makes you feel good and norepinephrine stimulates the production of adrenaline. Together, these chemicals explain why when we are around someone we are attracted to we feel a "rush" and our heart beats faster ((8)). However, if you have ever been in love, you know that these feelings somewhat subside as you become more comfortable with someone and move from that attraction and "lust" stage to love.

But what is the role of the brain in the stage of love? One chemical, oxytocin, plays an important role in romantic love as a sexual arousal hormone and makes women and men calmer and more sensitive to the feelings of others. Physical and emotional cues, processed through the brain, trigger the release of oxytocin. For example, a partner's voice, look or even a sexual thought can trigger its release. Attachment to someone has been linked to chemicals released from the brain known as endorphins that produce feelings of tranquility, reduced anxiety, and comfort. These chemicals are not as exciting as those released during the attraction stage, but they are more addictive and are part of what makes us want to keep being around that person we are in love with. In fact, the absence of these chemicals when we lose a loved one plays a part in why we feel so sad ((8), (9)). But is that it? Are chemical releases triggered by the brain when we think of or are in the presence of our partner all there really is behind those "I love you's"?
sources of reference:http://serendip.brynmawr.edu/bb/neuro/neuro03/web2/csmiga.html

People who are in love will have emotion cloud their judgement. Unconsciously, they let their heart make the decision instead of their mind. It can't be help and it happen a lot. Even the smartest person cannot be the smartest when it come to love. That show how strong the power of love can change a person.