Being the only one can be reassuringly good as much as it is terrifyingly bad. When you are the only one for your significant other, that feels great. You are proud of being loved and cherished that much. Your significant other is not looking for fulfillment from someone else. That's because you are enough for them. This is important because no one likes to feel inadequate and unworthy or to be compared and replaced with someone else.
Being the only one becomes hard when you realize that you are all alone. Not to be confused with being single because you can be single, fulfilled, and happy. However, if you are on your own, with no one to talk to, share about your day with, vent to, or just hang out with, then that can be bad. No man is an island and we all need each other in life for support and encouragement. You cannot thrive on your own.
That's why it can be lonely at the top if it's only you there. Some people climb the ladder and isolate everyone else afterward. But they can only remain like that for so long. It always gets to a point where they need other people. It's vital to be independent and to work towards your success because no one else will put in the hard work for you. But remember that you can never make it on your own. Even big people need people to open doors for them and personal assistants to help them keep up with their schedules.
So there you have it, being 'one' can be wonderfully amazing and it can also be sadly lonely. We are all one in a special kind of way and we need each other. Check out our 'one quotes' that give different approaches to oneness.