<span style="line-height: 20.8px;">In the second of a four-part series, cleantech VC Rob Day shares some more hard-won investing lessons. </span>It's been a while since I've last had the chance to do so, but I always look to try to draw out lessons learned from successes and failures that I've witnessed firsthand in this sector over now something like 12 years of being a cleantech investor. In particular, over the past year or so I've gained a lot more of these lessons, for better or for worse. (Last week we covered exits.)