That is a great question.
I don't think planning to fail so you have a plan B all set up, gives you the wrong spirit or motivation.
I've always been pretty positive, so I don't carry a plan B around. But it is a good idea to be valuable in the job you have. Be on time, be positive, look for ways that help out, and if there is optional training available consider taking it.
I've been in insurance for 40 years. I started as an adjuster and while doing that I took tests and passed various exams to better myself and went to additional training when available. This keeps you fresh and valuable. One thing I started then was a program called CPCU (Chartered Property Casualty Underwriting) and its a professional degree with 10 tests. Each test is given every 6 months and it's difficult. I had just started this and passed 1 or 2 when I'd decided to go from field work ( insurance claims over a geographical area) and find a internal job. I found a inside claims job and handled paperwork and directing investigations etc. I also decided to continue the CPCU designation. I'd been in claims all my career and this degree is really one that Underwriters get. But I continued and did pass all the tests and got the degree and kept doing claims. I did earn a trip to Hawaii with my wife, so that was a great benefit.
Then one day I lost my job and I was 55 years old, now what? Well I looked and looked for work as an claims adjuster. Then after a few months, I found an Underwriting Job the same town and I applied. Literally I got a call with 10 minutes after I applied on line. It was this UW degree that got attention and I took the job. I've been at this job for several years and have very similar benefits ...
So sorry for a long story, but I guess that was my plan B.
I did not mention, but a strong faith in knowing that I am not alone and that this faith in JC always keeps me humble and knowing that I will be taken care of.