You buy an asset when it is priced low and sell it when its price goes up. In between you need to keep holding that asset and speculate which direction it might be going. This is how the basic trading thing works. I believe that is what you were trying to say?

Time limit is not important here. When you are buying low selling high, you are having a long term goal in mind and would be willing to hold for years to come. For example the ones who bought bitcoin at three digit prices of 600$/BTC are getting a 100x profit today by selling at 60,000$/BTC. This is applicable to all sorts of speculative markets - stocks, forex etc.

Right now the price is high, so not the time to buy. Wait for bitcoin to drop back to 50k USD/BTC.