I'm still in the market and things appear bullish.
However I'm really fighting the urge to just go to cash and sit on the sidelines until the next downturn.

Meh, don't sweat it. Both approaches can work. The only thing to remember about moving to cash is that it works extremely well, if and only if you have the nerve to deploy it when there is a rich opportunity set.

Imagine someone who bailed and went to cash the day of Mr Greenspan's "Irrational Exuberance" speech in December 1996. That was a full 3.3 years before the index peaked (in real total return terms), a lot of FOMO. That's justifiably a market call about which some would say "being too early is the same as being wrong".

Yet the market was back at the December 1996 level again in 2002 after 5.8 years, and 14.5% lower than the December 1996 level as late as the 2009 bottom after 12.3 years, again in real total return terms. Lots of opportunities to get in at a better level, if you are the sort to avail yourself of them. And that's just the broad index: if you consider all the myriad individual good opportunities you might reasonably pick along the way, there's nothing wrong with cash. Provided, of course, you can spot and act on some of those opportunities.

Jim