Well, it is true. The pain from having a relationship with a parent, sibling, friend or pet is almost inevitable. You will have to lose them all some day. Its depressing but it cannot be changed. If you think it would be better to limit your relationships in fear of the pain that comes from losing someone you love, I would do that. Its a lose-lose situation in the end. Have all of the fun and good times you want, but it will end someday, and you'll be left with emotions that I sometimes wish humans did not have to experience.
Life sucks.