Just to prove it's not impossible, from one of our students:
"If you are going to succeed as an instrument-rated commercial pilot, you need to be self-motivated and capable of making your own decisions and adapting to a high workload. Oddly enough, these same skills and mindset are needed if you are going to have any chance of passing your exams. In that respect, it's not the quantity of the information that ultimately will get you across the line, it's quality and the attitude you develop towards your training.
In my case, I started the course in November 2013 and completed in July 2014, passing all 14 exams on the first try over three sittings whilst being a 49 year old father of two and working full time."