Trading Strategies are not constant , it changes with time. If we think the particular method we were taught in the early stages during trading will still work for the market over time, we may keep on losing because the market changes with time. One particular strategy of trading can't be use all the time.
As the trading market is changing so it requires changing strategy to earn good profit from it. It is generally difficult to get profit without adopting new strategies in trading. Those who are able to develop strategies over time are generally considered profitable in the trading business.