I might have given off the wrong impression - I don't credit myself for the timing of selling stocks. It just fitted well. Also, trying to beat the market is a fool's errand, we can agree on that. Continuing to invest is absolutely in line with this logic.
Still, a loss is a loss. How does that not affect you? At least on a primal, emotional level?
Something it took me an embarrassing time to realize in the early days - the stock prices may fluctuate, but the amount of stocks/mutual funds I hold remains the same. I know they'll eventually recover and then surpass the current value. As long as I'm able to buy more at a steep discount, why on earth should I be that upset? Sure, it can be a bit scary to see the drops in the early days, but I am one of those people that track daily, and I've seen so much volatility over the years I've been checking that I'm desensitized to the on-screen $ dollar losses. And I do mostly get excited to see the market go down so I can come up with a bit more cash. It's a win/win for me - happy when they go up, and now happy when they go down since they're on sale.
I also know that I will never need every single penny in my investments at once - at most I'd need monthly (cut to the bone) expenses, so I know that most of my portfolio will remain intact and able to recover from just about any serious scenario since I'm an index investor (as long as there are no doomsday/zombie apocalypses, I mean).
I used to think like the average investor - confused at how it all works, sure I'd never be capable of handling my own investments, scared of losing everything, and thinking it's all best left to the financial gurus.
But I'm much better now. :)