Why is the quote, " Love looks not with the eyes, but with the mind, and therefore is winged Cupid painted blind" so important?this quote is found...

This quote is important for a couple of reasons.  First, it is
an example of a heroic (or rhyming) couplet--two lines of poetry that have end
rhyme. 

As for the meaning, the quote is important because it
represents one of Shakespeare's many ideas about love, and Shakespeare is often considered to be
an expert at getting to the heart of human emotions.  This quote is basically the adage, "Love is
blind."  What he means is that if you love someone, you generally love them not for what they
look like, but for who they are inside.  Out of context, the quote is quite romantic.  In the
context of the play however, the quote is quite ironic; later Titania will fall in love with
Bottom after he's been given a donkey head.  Bottom's character is not admirable, so there is
really no reason--heart or mind--for her to love him, and that's where irony enters the
situation.