Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why invest for the long-term rather than buy and sell for quick, big gains?
If they return to their earlier prices Assuming I don't make too many poor choices That's your problem right there: you have no guarantee that stocks, will in fact return to their earlier prices rather than go down some more after the time you buy them. Your strategy only looks good and easy  in hindsight when you know the exact point in time when stocks stopped going down and started going up. But to implement it, you need to predict that time, and that's impossible. I would adopt a guideline of "sell when you've made X%, even if it looks like it might go higher." Congratulations, you've come up with the concept of technical analysis. Now go and read the hundreds of books that have been written about it, then think about why the people who wrote them waste time doing so rather than getting rich by using that knowledge.