I remember running a retirement plan for someone years ago and saying, "This only works if everything goes just right."† I don't know what your life has been like, but in mine, it is not often that everything goes just right. Some things do, for awhile. But most of the time life is about adjusting to things you didn't plan on.
Retirement isn't all that different. Something is going to come up that you didn't think of. And when it does, you better have a Plan B.
In the Retirement Management Analyst designation, we learn to account for Plan B by holding reserves for potential household shocks. This means not every dollar you have should be designated as available to provide retirement income. Some money should be set aside. It is part of your Plan B.
I also like home equity and reverse mortgages as Plan B. Reverse mortgages have an unwarranted bad reputation. They are a great tool when used in the right situation. †(See Reverse Mortgage Pros and Cons.)
Lots of people with decent equity in their home count that equity in their mind as part of their retirement assets. I don't like to do that unless it really makes sense - such as if the home is quite large and you know for a fact you will be downsizing.
If you have a modest home that is paid off, I like to think of that asset as Plan B. If you are healthy and need income later in life it might be tapped through a reverse mortgage. If you are unhealthy and need medical care, the home may be sold to unlock the equity. (Still have a mortgage? Read Should I Pay Off My Mortgage.)
So that's my preferred strategy for Plan B. What's yours?