Starting from the sentence "even though you only give 50% of your heart, I will still give 100% of my heart to you". Imagine, behind this sentence there is a cruel intention.
A mother's love for her child is so that her child can take care of her when she is old. Children to their parents is to get toys. Men's love for the universe is so that they don't get wrath and hell.
There is no original love without strings attached, as said as equivalent trade. Your love is definitely a payment to get something of equal value, or even greater. Ask yourself, what reward do you want from giving love to your lover. You name it, hand in hand, hugs, kisses, even sex, you pay for all of that with a payment instrument that you call 'love'!