Mac: If your computer or something you're dealing with on the web has you irritated, CalmDown can help you take a deep breath, relax, and move on with your life before you dive into a flame war or send an email you'll regret later.
CalmDown sits in your menu bar, and when you need to relax or you're just really stressed, click the Yin-Yang icon in your menu bar and select "calm down", or a series of deep breaths. If you select "Calm Down", your Mac's display will fade to white for a moment, encouraging you to take a deep breath or look away from the screen. A moment later, it'll come back into focus. Select "5 deep breaths", and the screen will do it again, just alternating colours for a good five-count before returning to normal.
The app is $0.99 in the Mac App Store, which may seem silly when you could just walk away from the keyboard, but considering how contentious rapid-fire debates on the internet are and how often people send emails they wish they could take back, it might be worth it to save your sanity.
CalmDown [Mac App Store]