Of course, it is worth it to take the time to think carefully through your assumptions, and ensure you at least have hypotheses around how you will create value. But use the analysis as a way to focus attention on the most critical assumptions, rather than spend a ton of time massaging the numbers.

Anything that has low certainty or has a lot of impact should be tested early.

When we are looking at ideas, we really are thinking of three things. Are you doing something that seems consistent with the patterns of success? Are there reasons to believe you have or can access the right people to make it happen? Can we play a unique role in enabling success? We all have our rules of thumb, I suppose.

Successful strategies adhere to a basic pattern.

There is what Steve Blank calls the stage where you are searching for a scalable business model. Then, there is the stage when you have found that model and need to scale it. In the former stage you have to have a "beginner's mind," be in learning mode, and expect to learn things you didn't anticipate.

Some people who were central to former success aren't the right people for your future success.

I've always found that working through ideas in written form really changes the thinking.