Once again, yes it is may be true that there is chance that you can sell higher if rumour is true. But if you base on discipline, you will find that 8/10 times you will be profitable if you sell on sudden price increase. As it is always it is — stock market is driven by rumours. Driven by fundamental, you will be sitting away from profit. As Buffett always emphasized, only discipline make you richer. It is not rocket science to invest in stock.