Progress , as general david petraeus , the american commander on the ground , is wont to say , is " fragile and reversible " .
美驻伊负责人大卫将军习惯性地称进展是“脆弱而可逆转的”。
The founders of companies that come out ahead in this battle often prefer to enjoy their new wealth rather than become serial entrepreneurs , as successful silicon valley folk are wont to do .