Very often, scientific breakthrough turns out to be an accident.  Here is another example of how play and fun mood can lead you to great discoveries. 

In fact breakthroughs must disrupt the logic of what we know; because they bring new knowledge, breakthroughs can come only from parts unknown to the conscious mind and therefore unknown to reason. So breakthrough — even the most intellectual and sophisticated ones – can manifest only at times when we disengage from what we know and from what we understand logically. This is why play is so crucial: it disconnects us from reason and logic and opens us up to new and different thoughts we wouldn’t otherwise have access to.

An 18-Year-Old Intern Who Kept Screwing Up Brain Surgery On Mice Accidentally Stumbled On A Scientific Breakthrough