Is it true that we only love one in our lifetime? it depends on what love means…. There are two different kinds of love: individual love, which lasts forever, and the love we invest in relationships…
The first one mentioned… well, we’re born with it : it represents our total capacity to offer affection and interest, with no expectations for a reply. It’s part of our nature of a human being, it defines our personality, it’s what makes one seem ‘affectionate’ and other ‘cold-hatred’. It’s somewhat a passive love. We don’t make an elaborate plan to send our love.. it just bursts out of us.
Still, the second type of love is different. It’s more selfish, definitely more based on a reply, on interests. In a relationship we give love, in hope that we shall receive something in return… like respect, affection or gratitude. We never invest feelings without asking something in return. Some call it selfishness but still, the cases where people offer this kind of love without asking anything in return are pathological.

Now... think about it for a moment... you weren’t that altruistic when giving you love in a relationship, were you?!