This was originally an answer I posted in a Quora group, but I thought I would repost it here with some edits. Read the original, in context, here.
After working with and owning several startups, it is clear that startup owners regularly overload themselves with work. It’s part of the startup mythos. The problem is, overwork kills lots of startups. The pace set is unsustainable and the endeavor collapses.
A few very important things where Lean Startup can be informed by Lean Lean.
First - Limiting work in progress is key to finishing things. You can't do more work than you can handle.
Second - Visualize the work - get it out of your head. There are too many variables and too many changes in context. You can better manage what you can see.
Third - Manage the flow, not the tasks - you are a startup, you will always have tasks. Working yourself to death will only result in your death. The flow of work is what is important - what can you produce, at what rate, and of quality.
Fourth - Kill Lists - Lists lack context, they age-out within hours, they leave you with no reasonable record of work done. They are the index of a map - even if read the entire index, you'll never understand the terrain.
Fifth - Prioritize Last - Making a long list and prioritizing up front is un-Lean. Most of your listed items will change in substance and priority as you do your work. With a visualized system, you prioritize / select work on-the-fly.
Sixth - Learn Cynefin - Understand that you will never know which of your tasks are simple, complicated, or complex. Some of them will bite you in the ass. If you outsource a task and think it's simple, but it is complicated or complex, you will end up working harder to manage the contractor than you would have doing the work.
Startup work is inventive - it is creative. Spend your time inventing the product and not reacting to the workload. Again, as Adrian said, this may mean some long days, but don't overdo it. Your brain is the only thing you have to make money from here. If you overwork it, it will underperform for you.
So learn from Lean, set up a Personal Kanban or any other type of kanban, and start visualizing your work.
Steve Blank says "Get Out of the Building."
I say, "Get Out of Your Head."