Timestamp: before the fall of the last human.
(I will leave those in order for you to keep track on when something happens or settled since some things might change drastically depending on time or even timeline.)
Look at where you are...
...Look at where you started.
Sans has a special place no one is supposed to know about. It's like a little gospel with a wonderful, but dangerous in wrong hands secret that better stay hidden for now. He will find a way to use it properly someday.
He keeps some of his secrets there, too, the little pieces of his past since nobody but him can go there. Mistakes and regrets, mostly, but... those are also his most precious memories.
He isn't supposed to look back, he must look forward and help others to do so. It's his purpose. But... just sometimes he needs to go and remind himself who he were, what he did... how he get where he is now, and not to let himself do the same mistake. He isn't sure how, but he thinks he will figure it out if the moment ever comes.
Contradicting, but the moments of his own failure give him strength to work further and... literally, stay alive. If he looses any more hope...
No. He won't. Since nothing changes down here, he will just keep the routine and slowly but surely 'light' monsters' life, like he did Monster Kid's the other day...heh.
