I came across this tidbit in an article by Seth Jayson over at fool.com (subscription required to read the article) and it made me reflect on my own yardsticks for success:

The trouble for investors is that we tend to judge our success based solely on the outcomes and not on the processes. Thus, a well-reasoned thesis that doesn’t work out becomes a failure, and a brainless, lucky bet on an unlikely growth stock success becomes genius. In the short run, the lucky money feels good and spends better than the intelligent loss, but over the long run, the unthinking luck is going to run out.

I think one of the most important things to remember as an investor is that the process is much more important than the outcome so long as you are sufficiently diversified. So make sure that you go through the process of establishing why you are buying a company every time.  Keep a journal and write down your thesis.  After your thesis plays out (or, as I’ve experienced, fails spectacularly), go back and review what went wrong.  But never beat yourself up for a bad decision if you went through the process.