Everybody wants to live forever, but they seem to misunderstand mortality. Your life has meaning because of the inevitable. You strive to do the right things and give your life purpose because it's short. Your career gives your life importance because you need to earn and enjoy your life while you can.
The thrill of life and love would be lost otherwise. A relationship has the thrill that it does because there's so much to do and so little time. You never know when things are going to stop working out, or maybe you find passion amidst a dying relationship.
People want guarantees, but if we had them, we wouldn't be the same. There'd be nothing special if everyone's handing out guarantees. In an ideal world, it would work, but not in this one.
The risk is what makes things worth it. Remember that and appreciate what you have instead of being sad that it won't last forever. The truth is that nothing lasts forever, including us.