I own and have owned many businesses in my life. Some were failures, but many were successes. After thirty years of diligently practicing this game we call business, patterns begin to emerge. When looking back, it is easy to see what I did right and what things I did that were downright stupid. I can state without any hesitation that every successful business I wound up with were successful because eventually systems were created and implemented. Based on that, I would argue until the sun goes down that if you want your small business to really be successful you need to start creating, documenting and implementing systems.
Keep in mind I always distinguish between being self-employed and being a small business owner. Neither one is necessarily better than the other. If your desire is to keep everything simple, never hire more than one or two people and to always be the main producer or service man, then being self-employed is a much less stressful way to go. But as a small business owner, the business will take on a life of its own. Like a child it needs rules to regulate how it acts or before you know it, the spoiled child will take you down, hard! Systems are the rules for your child.