Buying low and selling high is a simple strategy but then the price direction is highly unpredictable, so your analogy may not be accurate at all times since Bitcoin price cant is predicted, ask yourself what if the price goes opposite what you proclaimed in your trading strategy.
Am not a passive trader any ways am more of a holder than a trader and i will say it is better to buy low and hold for long time and again ops that your 30% calculation is inaccurate considering Bitcoin present position.
Have a good strategy on analyzing and you can be good, right now TA works and those traders who are responsible enough are already winning on this bear market. Trading works and it can be more profitable if you do it perfectly, though its really unpredictable but if you have strategies to counter that, there’s still a higher chance for you to get the profit. If you have more funds to catch the bottom, that’s better.