Ok. So I actually got really lucky when I learned this.
When I started my pet supply and service business, I thought I had done all the proper discovery work, so I had the idea that we'd open our doors and without any advertising whatsoever, we'd be flooded with business. I did something unconventional that worked to get passers'-by attention, and I'll share what I did in a later post, but nearly everyone that stopped in the store asked the same question -- "Do you do grooming?" And when I told them we didn't, they said, "Cute place, but I need a groomer."
Admittedly, the thought of offering grooming hadn't even crosse my mind. I opened up as a self-service dog wash. We had the nice tubs, warm water, all-natural shampoo and conditioner, towels, brushes and blow dryers. I offered a few toys and treats, but the bulk of my space and of my focus was dedicated to the idea that people wanted a cleaner, easier way to wash their own dogs where they didn't have to spend hours afterward cleaning up the mess.
My wife and I used up a good portion of our savings at the time to build out the store -- roughly $40k. When it became clear that we had missed the mark on the main service the people in the area wanted, we had a big decision to make: continue to operate in our originally conceived manner and try to expand our market to pull people from outside the area, or to reinvest to change the setup and focus of our business.
We chose the latter, and this is where I got lucky ... You see, while I hadn't planned for failing by not really understanding my market's main desire, we had been very frugal and efficient with how we spent our money when we opened, which meant we had extra savings to make the necessary change to accommodate the market's desire for full-service grooming and high-end dog foods. We built a serviceable grooming area and invested into shelving and stock for a variety of dog foods.
For the next three-and-a-half years, our business grew and grew, and if I knew then what I know now, I may never have sold it (burnout is a real struggle and one every business owner should plan for -- but again, another post for another time).
The takeaway from my story, here, is no matter what you get in to business to do, plan for failure. Don't use all of your money just getting off the ground. And set aside a portion of your income from the business so when you run into those areas where you aren't serving your market how it wants to be served, you have the flexibility to pivot.
Plan to fail so you're not caught off guard and have no options for responding when you do.