"we're not exactly at the point of maximum pessimism just yet"
That's right, we're not. Just because the stock market went down 2% yesterday doesn't mean that it's now a screaming buy. The VIX currently stands at 19.11, almost exactly in line with historical averages. Markets are only down about 5% from this year's high. When the market is down 20%, and the VIX is at 30%, THEN it's time to fill your boots. We're a long way off from that. Maybe a long way off - years away, perhaps.
So, how lucky do you feel with your market timing? If you're a market timer then now would be a good time to sit on the sidelines. If you're not, then all the time is a good time to buy shares, and you can never take advantage of market swings, because you're fully invested.