The Fear of dying alone.
That's right, it is real and it is a very valid state of mind. Humans are social "animals", by nature, therefore they always tend to worry about lonesome when they are faced with isolation. Well, that's the case with the majority of human race, unless you like being alone, and even then, you will like it for a period of time then will be lured back to people, once again.
Socialising has its benefits, and disadvantages. It can be a very rewarding journey, or a tiring one. Depending on how you are doing it, and with who. I am not going to tell you, I am an expert in social communications - sometimes, i go years without talking to people within my circle. However, that does not make it a vital factor in the human life - finding the right people, and making social connections that will prevent you from having "monophopia".
There is no guideline on who you should talk to, and how will they look like, not in my books anyways. But, a simple rule to follow is: surround yourself with people who will make your heart happy. That does not mean they should be happy one hundred percent all the time, rather they make YOU happy all the time. Even through their darkest days, you are still happy to have them around you. People who you will call "friends", not just "people I know". Those are the ones who will fill your voids, and make your life complete.
Spiritual fulfilment is another topic, by itself. But, briefly put, it is seen to be a vital factor in having a supportive, and happy relationships. They should be comfortable with being with yourself in order to enjoy the company of others. It's like the saying goes "you can't love others, unless you love yourself". Unless you enjoy your own company, you will probably never get satisfied with company of others- no matter how good they are to you, and your soul. Do things that will make you at peace, and have serenity. Do those by yourself, first, and enjoy doing them. Then, and only then. look for companions to share those moments with - just make sure, those companions are worth your time and energy.
Being alone, is not always a bad thing. Sometimes, we need to be alone to have some "us" time without the noise of the outside world. Sometimes, we enjoy the company of nature over people, and the written word over verbal communications. There is nothing wrong with that, on the contrary, it is considered healthy to take a break from "others" every now and then, and indulge with a journey with your inner self - it is part of mindfulness and meditation. What could be alarming is when you are alone, but you are sad and fearful to die by yourself. Then, you need to get out there, get yourself new friends and talk to people. The earth is vast, with so many humans living on it, I am sure you will find at least one to talk to - if not, you can always come to me :)
Take care of yourselves,