Well stated Eric, as we go through life our needs change for income, as well as the urge to gain/accumulate more. The latter will have more risks also. When one is during their earnings/employment years it is time for a little more risk for the sake of more accumulation.
Later in life we cannot afford a years long Bear Market, when one should not withdraw money from the portfolio, but look for opportunities to invest at a good price.
As we age it is also a good idea to keep liquid assets for about 9-15 months, still earning on it, but much less risk.