My one regret is that I always split my account into broad market stock funds and bonds by a fixed percentage (i.e. 70/30 split in favor of stocks, for example). When the market tanks, I sell bonds to buy cheap stocks and get the ratio back. When it skyrockets, I sell stocks and buy bonds to keep the ratio right. In doing this I'm selling high and buying low, always. If stocks tank, what's left?
But my wife dragged me to a family friend to review my simple portfolio and he talked me into significantly upping the percentage of stocks. I did it at the beginning of Summer, sold a bunch of bonds and bought stocks. Which means I bought high. And now it's lower and I have not much in my bond fund to sell to buy them low. I really screwed up my plan by listening to that guy. In his defense, the bond funds were making bupkis. So I definitely had too much of that.
Honestly though, if we entered into a sustained bull market I don't know where money can go anymore. Bonds are terrible, real estate isn't so great either.
Should read "bear market", not bull.
I can give you only one piece of advice with respect to investing: Know yourself!
Know what your psychological limits are.
Know how to control your impulsiveness.
Learn how to recognize when you've "fallen in love" with a stock (a big no-no, as I'm sure you know).
Know how greedy you can be.
Learn to catch yourself when you fall prey to "magic thinking."
Knowing your investing horizon is a very good starting-point - but it is not the end of wisdom.
Regards,