<prompt> Human: Ive been trying to subscribe to the index fund philosophy of investing, i.e. regularly contribute money to an index fund representative of the market, and forget about it. Over years and decades, this is most likely to give optimum returns with minimal expense ratios. I do this with a retirement account and a brokerage account.Does it make sense to intermittently book profits, when you see the market over-valued? I wont be touching the retirement funds, but does it make sense to do so with my brokerage account? Thanks for listening!  <response>: Well, you can rebalance your investments. If your goal asset allocation is 80 stocks and 20 bonds, and the stocks go up so that they are now 90 of your portfolio, its reasonable to sell some stock to bring yourself back to your goal. 