icedchai summed it above but the reason for this isn't to maximize return - it's psychological. If the market drops, you now can buy more at a cheaper price. If

icedchai summed it above but the reason for this isn't to maximize return - it's psychological. If the market drops, you now can buy more at a cheaper price. If you spent it all, you probably would be tempted to cash it all out to cut your losses. of course, you shouldn't, but we're talking about our lizard brains here.