What is "bad" is reverse-position sizing, taking your largest position at the start and then "peeling contracts off" as the trade goes your way. Tharp mentioned this in his first "Trade Your Way To..." book
He did indeed.
And it's troubled me, intermittently, during the decade or so since I first read it.
It's an interesting opinion, and it certainly has
some validity,
some of the time, for
some trading-methods.
It
isn't "factual" or "objective" (though the way he words it makes it appear that way).
These three things, however,
are factual and objective ...
1. There are also some serious, successful, professional, institutional traders who routinely do exactly what Tharp's advising against, there;
2. Some other authors of similar stature and reputation disagree with him about that point, and have said so in books published since his, some of them even quoting him directly and explaining the reasons for their disagreement;
3. What he explains rests on the
assumption that at the time of entering the trade, there's
less probability of its being successful than there is, later, of its continuing to be
further successful after an initial price-movement in the direction of the trade - and this
is an assumption, and not a fact: certainly it's
sometimes true, depending on the method of trading, but
by no means always.