The answer here is heavily dependent on how you define your success for the program before even beginning.
A general definition of success could be continually moving in a direction that improves your company. There are many ways to measure this, and this is up to you as the founders to decide what works for you. I have a couple of suggestions for measuring your success during the three months and beyond;
Firstly, start tracking your progress and everything you do at your company. It’s better to have an excess of data than none at all. You’ll be able to make business decisions based on facts, and will be able to quickly see your progress including where you need to improve. There are a number of project management and workflow tools you can use to start tracking your business, as well as endless analytics tools available either for free or at very reasonable prices. You’d be surprised how at ease your mind will be once you start doing this, and how much extra brain power you can allocate to other tasks and worries.
Secondly, you can also create your own checks and balances, as a founder and as a team. In periods of high intensity, it’s very easy for these to be the first things to go. Creating a habit of leaving time aside every week for reflection will allow you to make informed decisions and iterate faster, with a clear vision and solid explanations for each decision. I’d suggest following the intellectual honesty and openness Techstars has built into their own company culture and building it into your own company culture.
You can also read about the checks we've built into the program content (as investors) to make sure we're doing everything we can to help you achieve success.