Don't chase every opportunity
Do not try to net every bird that passes. A merchant who grabs at every deal spreads himself thin, so he should choose his ventures rather than pursue all of them.
Business
Lost time is lost money
For a merchant, losing time and losing money are the same thing. Delay, idleness and slow decisions carry a real cost that belongs in his reckoning just like a bad sale.
Profit serves preservation of mankind
Trade exists first for the preservation of mankind and only then with hope of gain. Profit is legitimate because the exchange of goods keeps people supplied and alive, which makes the merchant indispensable rather than merely tolerated.