First: what's your risk tolerance? How long is your investment going to last? If it's a short-term investment (a few years) and you expect to break even (or better) then your risk tolerance is low. You should not invest much money in stocks, even index funds and "defensive" stocks.
If, however, you're looking for a long-term investment which you will put money into continually over the next 30 years, the amount of stock you purchase at any given time is pretty small, so the money you might lose by timing the market wrong will also be rather small.
Also, you probably do a remarkably poor job of knowing when to buy stocks. If you actually knew how to time the market to materially improve your risk-adjusted returns, you've missed your calling; you should be making six figures or more on Wall Street. :)