Start up is a unique phase in every business and every business has gone through it. Starting your own company usually means that unless you are in a partnership or have REALLY good connections you will be doing EVERYTHING in your fledgling enterprise and probably with limited funds. Also the person you meet up close and personal is... yourself!
You find out how easy you are to manage and where you will hide in order not to do things! And your success will depend on how you deal with your internal as well as your external blocks. Coaching someone through this phase is a delight and something I enjoy immensely.
And when someone finally 'gets it', i.e. what entrepreneurship really means, then you hang onto your hat because you know it's going to be a wild ride.