Ahh. Market timing. Or, as I used to practice it, both catching the falling knives and buying on the peaks. Neither worked well.
SEC.gov | Beginners' Guide to Asset Allocation, Diversification, and Rebalancing
YMMV, but for me the practice of selecting an asset allocation, filling it with index funds/ETFs and rebalancing once a year has produced good returns, low fees and low stress.