Never add to a losing position. The news always follows the market. To buy on a rising market is a most comfortable way of buying. Buy on a scale up. Sell on a scale down.
Commodities are never too high to begin buying or too low to begin selling.
But after the initial transaction, avoid make a second unless the first shows a profit. The principles of successful commodity speculation are based on the supposition that people will continue in the future to make the mistakes that they have made in the past. Don't pioneer highs or lows. Let the market tell you a high or low has been made. Except in unusual circumstances, get in the habit of taking your profit too soon.