Coming from a Gamasutra interview with dev Edmund McMillen...
"There were a lot of subtle elements in my past platformers that I never fully explored because I was worried about alienating the audience. I wanted to make a game that was honestly a bit uncomfortable to play for people who have issues with stress. I wanted to make a game about stress, pressure and expectation. I feel like I was able to do exactly that in simple and elegant ways I'm quite proud of.
In the past, people would say my work felt like a love letter to classic video games. I wanted The End is Nigh to walk the line of a suicide note or retirement letter. Its themes really are an abstract tale of the dark side of game development - the lonely, stressful, paranoid dregs of the creative process.
In the past 3 years, I've faced some very difficult personal hardships. Just when it seemed like the end was in sight, something else would come up and drop me even lower than I already was. The End is Nigh started as an exploration of this, but as it unfolded, it really became a story about my personal struggle with game development, my obsession with my work, and how it affects my family."