Time in the market beats timing the market. If you continue to invest regularly even in a down market you will eventually make more than those who target peaks and dips.
This was shown to be the case in a mean-variance framework in 1979 by George Constantinides [0]
[0] https://papers.ssrn.com/sol3/papers.cfm?abstract_id=148754
This has merits in a bull market regime. However, we may not in a bull market: history suggests that we will have a deeper bottom within 3 - 12 months. So if you buy stock now, when the market is within 10% of it's peak, and you have to wait for two years for the market to recover to that peak, there's plenty of time for someone to wait for the trough and substantially outperform you. Hopefully you are at least collecting dividends, but 2% is a small solace for spending 30% more than you would need if you were patient for a few months.
Bear Markets: This Time is Different (Every Time) - https://www.youtube.com/watch?v=Jh9Gn58r9Fw
There's been countless examples of projecting returns for an investor who tries to time the market and one who keeps buying and almost universally the timer loses.
FWIW, I haven't sold anything, but I haven't bought any shares either since the beginning of the crisis. I would be wealthier today if I had kept buying on my normal schedule.