Earlier quoted context omitted.
Timing the market is hard but periodically rebalancing your portfolio is easy, and generally recommended.
Rebalancing according to risk is recommended, not doing it because you think you know what the market is going to do. For instance, let's say right now, the market is headed up. When is the right time to "re-balance" to more cash? This is just assuming that the market is going to go lower than it currently is, which is just as much a gamble as thinking it'll go up for the next year. In short, don't try to guess the m…
When you look at your balance at the end of the year and your cash proportion happens to be below 20% instead of 25%.
Rebalancing is pretty much standard practice nowadays, nothing magical there. Any financial advisor will tell you to rebalance your portfolio from time to time.