Throughout any given day, my mood & state of mind fluctuates depending on many factors: quality of sleep, what I ate that day, how my personal relationships are going, how my company is doing, etc.

Because of this, I try to avoid a fixed schedule as much as possible. I view my day as fluid: I have a collection of different states of mind throughout the day, and I have a collection of work items that need to be done, so I try to match these up.

When I'm feeling creative, I write code or do frontend design. When I'm feeling insightful, I think about longer-term company strategy. When I'm feeling extroverted, I focus on user outreach and customer conversations. Mapping my states of mind to the appropriate deliverable lends itself to my best work. The opposite is also true - forcing tasks in an improper state of mind often produces worse results.

This is a simplified view - it certainly won't be possible in all jobs or on all days - but I'm fortunate enough right now that I'm able to abide by this as much as possible, given that an early-stage startup has time spent mainly between building and talking to users (and both of these have a spectrum of sub-tasks that tap into different states of mind). This is in contrast to my time spent at Google, where I often had days filled with back-to-back meetings.

Deliberately not working is also important. If I'm feeling awful and particularly unproductive, I prefer to make a conscious decision to step away and rest, in contrast to making little progress on something while beating myself up over the lack of productivity.