We don't thing negative like that.
Exactly, especially because there's no guarantee this won't happen when you meet the girl and she's been solo.
Imagine, you meet a fine girl but she dates a dork for a few months now. Sparks fly and you start spending more time together.
Would you stop because she has a bf, especially when she tells you how sad and unsatified she is? Never.
The key is to care about your partner, every day of your life. Every hour, every minute. Be there when they need you, give warmth and shelter in bad times, fun and laughter in good times. And when it ends, it ends. Nothing is forever, and we all need to learn how to let loose of things that go away. Friends go away, parents and loved ones die, your car gets wrecked, things go away, that;s life.