The biggest problem I encountered in my application was stress. I was only applying to one school because of reasons, and if I didn't get in at that school, I had no idea what I was going to do. I also needed the assistantship, and wasn't sure if I was going to get that or not. On top of all of that stress, I got let go from my job of over four years (that I had hoped would last me until I needed to leave for grad school). I had originally wanted to have all of my application materials in before the new year, but ended up getting them in closer to the end of January, two weeks before the deadline.
Luckily, I got in with the assistantship, and the cat we adopted really helped with the stress, but it was a lot of hard, emotional work. Writing the materials wasn't that stressful, but writing them with a looming last day of work and nothing lined up after that was.