The process of growing a business reminds me of the old saying "It's fortunate that youth is wasted on the young". I believe it refers to youth's lack of wisdom when they have the vigor. A new business begins with much vigor and little wisdom (at least mine did), and progresses to having much more wisdom while the vigor turns to resolution and determination. "If I only knew then what I know now!" is a different way of saying the same thing. Despite the vast amount of written words about starting and running a business, no amount of studying can teach the hard lessons you take by just doing it.
This is not an argument against preparation and planning. I am a student of small business and business history. I read all I can about the subject, always looking for something I can apply to my business. I suggest you study and prepare well before you begin. But it is like the difference between knowing the swimming pool temperature and jumping in — that first plunge is still a shock. But you will get used to it. If you don't, you get out or drown.
There is no magic formula that guarantees success. Only your resolve will keep you in the game. That's fight. It's not your ideas or your money or your partner. It's your resolve that you know you can grow a successful business despite the incredible odds and Tury's First Law of Business which states, "All forces work against your success".
Pessimistic? Not really. Just a realistic way of saying that the universe tends toward increasing entropy and chaos. Your task is to organize a small part of the universe into a profitable smooth running business which is just opposite to natural forces. I have come to believe that one characteristic of a successful entrepreneur is a firm belief in Murphy's Law. It will make you careful and observant, two useful things for success.
Speaking of entrepreneurial characteristics, I find it interesting that the old wisdom said that one had to be a wheeling, dealing risk-taker to start a business. The new wisdom says the opposite. One should be a risk-averse planner. Well, baloney. You'll find all manner of personalities in business for themselves. As I have said before the characteristics needed to grow your own business are the ability to live with uncertainty and the refusal to quit. Living with uncertainty is not the same as risk-taking. Sure things often aren't — see Murphy's Law.