Yea you are right, I understand what you are actually saying, but I believe that as a trader, the most important thing is the quality of trade you take, than the quantity.

What he is trying to say is that each trade comes with it's own risk, their are higher risk trade, their are also lower risk trade.
Their are trade were you spot the signals very clearly that it's a must win trade, and those kind of opportunities mostly comes in the market, but not always, so I believe that in other to be successful in the craft, it's best to be patience enough to wait for such opportunity than to be trading a market you aren't certain of.

Then lastly, one major reason why it's very important to take only quality trade is that, in trading you can lose all your winnings, even with your initial magin in a single wrong trading if your risk management strategy is not properly utilized, so it's best to go for a trade or a set-up you are only sure off, than to risk it on less quality trade.