There is a popular myth among those who are just starting trading that successful traders have many strategies that allow them to be very profitable all the time. That they can make a lot of money month in and month out by applying one strategy if the market is trending, another one if the market is ranging, one if there is high volatility and another one if there is low volatility. This myth, born out of the desire to have a constant flow of trading income is also perpetuated by shady vendors of educational services.
The truth is that most traders and investors have just one trading strategy, that they have developed to fit their own personality, and they stick to it. Let me give you a few examples:
1. Warren Buffet, the world’s greatest investor. He sticks to what he knows and does best, value investing. Can you picture him trading Eur/Usd off the 1-hour chart? Or day-trading tech stocks? He didn’t buy Microsoft in the late ’90 dot-com mania even though he’s good friends with Bill Gates.
2. Dan Zanger, who holds the world record for largest percentage gain in a personal portfolio, turning $11k to $18 million in 18 months. He is a technical stock trader focusing on chart patterns of fast-moving stocks. Can you imagine him buying and holding Coca-Cola or Gillette?
3. Ed Seykota, a very successful trend trader featured in Jack Schwager’s Market Wizards. Can you see him trade stocks the way Dan Zanger does ?
Just like a physician can’t be the best brain surgeon, the best psychiatrist and the best urologist, a trader can’t be a master of all trading styles. There will be times when your strategy will outperform others and times when the market will be less conducive to your style. Trying to be jack-of-all-trades will only lead you to mediocrity. To continue the parallel with medicine, can you imagine a psychiatrist who has no patient appointments for a week becoming a dermatologist overnight, just because his colleague has a full list? 
To conclude, no one can try to be a day trader this week and a long-term trend trader next couple of months and expect to have any meaningful success. To become a great trader you have to focus on one style that best suits you.