Humans are social creatures. We love company. We love companionship. This is why it would be difficult for anyone, if they were the only one left on earth.
If I was the only person left on earth, I think it would be a difficult period for me. I think about it and I realize that being the only person left means that I would spend days, weeks and months without seeing anyone to talk too. It would just be me and my thoughts.
Being the only one on earth also means I would have to do everything myself. Nobody to depend on. It would be incredibly lonely.
Imagine not having your loved ones around. No one to share things with. Life would lose its meaning. Life would lose its flavour. Anyone in such situation would basically lose their mind. That person would lose touch with reality.
One would just sleep, wake up, eat and repeat the cycle. There would be no purpose to life. There would be no reason to function. There would be no work to go too. The essence of work in the first place is to solve problems and make ends meet. With people gone, there would be no need for that anymore.
There would be no parties to go to. There would be no one to drive you if you don't know how to drive. I even wonder, how would one be able to get petrol for their car?
Who would import the crucial products I would need? Who would be in control of electricity? Who would do the engineering jobs? Who would treat me if I get sick? Who would bring the food?
The list goes on.
Life would just be incredibly hard. No one man can do everything himself. Without people, there would be no memories to make and hold on to.
In conclusion, being the only one in earth is the worst thing that can happen to a person. That person's mind could get fractured