As human beings, we are naturally afraid of failure. Perhaps it is a primal instinct that survived evolution, when failure meant death.
There is no doubt that becoming a business owner is scary! When I left a very nice job, many years ago, the one question that I was repeatedly asked was, "Why?" (I think they meant to say "Are you crazy?!", but were too polite).
Being an engineer, I had taken some precautions. We built a cushion of funds for 10 months via deferred salary/bonuses. I developed an excellent relationship with my employer as a fall-back (they actually kept my office empty for three months, hoping I would fail and come back!) . In addition, while I was still employed, I made it a point to inform all my future customers that I was venturing out. A surprising number of them assured me that they would help me get started.
Apart from the fear of not being able to make a living, there is also another deep emotion when you get out of the "safety zone". This is the fear that failing in your profession somehow indicates a personal shortcoming. This type of thinking has been termed the "Fixed Mindset" by a Stanford psychologist. Subscribers to this philosophy believe that we are born with some innate capabilities and cannot change. Thus, if we try something new and fail, others will find out about the real me!
To combat this, the Psychologist advocates cultivating the Growth Mindset: if you experience a failure, don't personalize it. Chalk it up to a learning experience and go on. If you start thinking like this, you actively seek out new opportunities and are suddenly not afraid of "looking foolish" or a "failure". It not you that failed, it is your attempt (this time) that failed - A CRUCIAL DIFFERENCE, my friends.
So, in a nutshell: take sensible precautions, but also get yourselves in the right mindset.