Getting scared

I am about to go all in on launching this business. I have the finances mapped out and it should be within budget but am going all in. Investing in a bunch of units and trying to launch. I am going to be using a marketing agency from launch, so I know its in their best interest to get me sales as fast as possible, but I am getting anxiety and scared to start the process because there is still a chance of failure right? I know its slightly less likely because I have a huge agency whose literal purpose is for this not to fail but still. Any advice as this is my first business?