Funny...I was just talking to my friend about this last night. She wants to get a pet in the worst way, but she's terrified of becoming too attached and not being able to handle the eventual loss.
I have had pets all my life and probably would feel incomplete if I didn't have one. What I told her was, basically, that even though losing a beloved pet is one of the most painful experiences, the joy and love that a pet brings into your life outweighs everything. Yes, we become very attached. Yes, the very thought of losing them is unbearable. What you have in return, though, is someone who is always happy to see you, who will never turn his back on you and who doesn't care that you're not perfect, and will love you anyway.
You also get to take a sweet little animal and give him a life without fear of being on the streets, hungry or mistreated. As with any relationship, you give and you get. The difference is, when you have a pet, you get so much in return and you can be sure that what you're getting is sincere and comes from the heart.
So I told my friend, even though they can't live forever, your life will be so enriched and you will always have the memories.