Sell into strength.
Those buying at higher levels are entering when a lot more is known regarding events unfolding, or they are playing the momentum. You're adding before the fact. Strategy vs strategy...they work in tandom and there are all types of investors employing their strategies and taking alternate risk positions.
The question is, how high is high?
$5 seemed high until it ratcheted to $10 in a blink of an eye.
$12 seemed high until it moved to $17....and even after $24.50 it held above the $2 mark for about a year before the long decent to current levels. So piecing your sales on the way up seems prudent, to partake in profits and further participate for any wild runs....and protect against any slide back.
Looks like were are not too far from having to make those decisions again.