Here's the deal. There is no forever. Life is long and then it's over. People come and people go. The security is actually in the freedom of knowing there is always another person, another job, another place. Humans are very good at adapting.
That little child inside you is still afraid, still feels small and helpless, but you can realize you are not small and helpless anymore. Once you stop trying to lock down forever that doesn't exist, you can choose to commit for as long as it lasts or you can choose not to. Rather than being afraid, you can realize that you choose.