A decent strategy could be to always sell the same amount of BTC.
When the market condition allows it, by buying using your USD profits the BTC balance will increase slightly. When this happens put the extra BTC aside, rinse and repeat.

E.g. if you start with 5 BTC and you end up after a trade with 5.13 BTC, put the 0.13 aside and keep selling 5 BTC.
Which means as I have already said, buy low, sell high and then buy again low(er).