I think the strategy you use is good. We should avoid selling coins with red market conditions, but the red market is a good opportunity to buy coins at low prices. But I also often try this strategy, but the coin price drops very sharply. And when the price is green and I will sell, but I still lose because the increase in the coin is not high.
But a safe strategy is not too greedy. With a little profit but we do not suffer losses.
Every strategy can be good, but there's no strategy that works in long run, you need to change strategy and try to adapt to the current market conditions. I can't say that trading can be completely safe, but with some steps you can lower the risk. Greediness is the number one killer, with that part I agree, doesn't matter on strategy someone is using, greediness is a money eater! Another step to lower the risks is patience, to not make sudden actions, be patient and wait for your moment, bitcoin is volatile and if you miss a good moment for something be patient and wait for next good opportunity.