Is maintaining cash flow by putting money in low-interest investments while waiting for big dips to invest in more aggressive funds a viable strategy?

I'd like to get thoughts on this strategy. I have all my investments in aggressive funds. However, I recently shifted toward putting new money from each paycheck into a low-interest investment (e.g., bond index,.cash account) while waiting for big dips to invest it in the aggressive funds. That way, I have the cash available to take advantage of stock market sales. Does this make sense, or am I missing something?