What product do you use to capture your day?

I use Day One, primarily on my iphone, to record my thoughts every single day. I have a daily reminder setup to help me maintain the habit. Day One let's you create different journals within the app, so I have a general journal to record the daily happenings and a separate journal for things I've learned.

Passion Planner is a diary which can really help you answer the "What did I learn today" question.

This is technically a tool for teams to quickly report all the things you've done as they happen. Out of the box, it sends you an email each day asking you what you've done and you can reply to add it to the list (or use their website, or just send an email to it). What's more interesting is integrating iDoneThis with Slack or other 3rd party tools like Alfred on Mac or even the command line to update your status making it accessible from just about anywhere.