You have to pick a niche. You are right about that. It is a hard problem as well because there is no guarantee and you need to spend at least 18-36 months before you really quit and move on to next idea.

However, you have 8 years of working for customers, building their products etc. Are you saying that you never came across a few problems within those 8 years that you would like to solve ? Start there. I am sure there are a few areas/problems that you came across. I have been running a SAAS product for almost 7 years now and I have written at least 25 problems that I would love to solve some day if not doing the current business :).