My biggest mistake in trading

I should have use rotation strategy with a bunch of stock instead of putting a bulk of my capital in one of the stock. The day I brought it, the next 3 days it dropped 15% my blood pressure raised significantly. When I look at the chart, the stock is trading at tight band with a 5% variance and slow change over the past 3 years. Lesson learnt.

1. Don't put all my eggs into one basket

2 . Select a bunch of stock

3 . Deploy in tranches