Market is down at present and i think invest as much as you can as after correction phase prices would surely surge and high profit is expected on return.Holding currently is another good planning to earn a considerable return as per your planning.If you sell your investment due to low prices you would not be able to receive much profit.To me currently both Investing and holding strategy are inevitable...
Those positive thinker they always did this strategy because why are you selling you bitcoin in the lowest price if you can hold and invest more for the future rising. You are right that now the value was low but don't be a negative thinker because even and now their is a possible for the rising, after falling down the value the next one was rising so invest amd hold now before the rising.