When it comes to investing, there seems to be a lot of contradictory advice out there. What's right and what's wrong? I addressed this dilemma a few years back, when I explained that learning to invest successfully isn't a straightforward endeavor. You'll frequently run across seemingly contradictory advice, and you may be left scratching your head. The solution is to understand that investing is both simple and complex. (See? Already, a contradiction!)

As you begin, investing can be simple. Your first steps should be to get out of debt, read broadly on investing, and perhaps invest your initial dollars in an index fund.

But, once you begin looking into picking individual stocks on your own, you may start to run into some of those contradictions. For example:

  • Don't waste your time trying to time the market. Always remain invested in stocks.
  • Don't be afraid to stay out of the market, at least partially, for a while. Wait for the fat pitches.

Here's another pair:

  • Don't add money to a falling stock position.

  • Engage in dollar cost averaging -- investing regularly in a stock no matter whether it's up or down.

There are many such predicaments that frustrate new investors. Imagine that you own shares of Merck (NYSE:MRK) and see its price falling because of problems with one or more of its drugs. Do you buy more -- or perhaps even sell? It depends on your evaluation of the company and your confidence that it will recover. If you owned Intel (NASDAQ:INTC) some years ago, when a faulty chip caused its shares to slump, you'd have made money by buying more shares. But if you bought more of Kmart (NASDAQ:KMRT) as it fell, back when its ticker was KM before it emerged from bankruptcy protection, you'd have lost money. Aphorisms can guide you, but you do need to conduct your own research and thinking.

Here's another common contradiction:

  • Buy with the intention of holding forever, or at least for a very long time.
  • Sell when something much better comes along.

And:

  • Let your winners run.

  • Rebalance your portfolio when one or more stocks come to dominate it in a big way.

Most Fools will agree on some points -- penny stocks are bad, technical analysis is dubious -- but there are many other points on which we'll differ a little. Furthermore, scratch the surface of a Fool, and you'll likely find that many of us are a little contradictory even within our own attitudes. That's fine. It just means we're complex, and that investing can be complex, too. In some situations, buying and holding for decades might work well. In others, it might make sense to sell when something much more promising comes along.

If you're a good Foolish investor, you're always questioning, examining, thinking, and rethinking. You're continually changing your perceptions of investing, perhaps after making some regrettable moves and pondering how they came to pass.

  • Life is simple: Eat, drink, breathe, sleep.
  • Life is complicated: Prepare a tax return, study physics, raise children.

Wherever you go, even in investing, you'll always find contradictions. But that's OK. Really.

Learn more about investing in companies in our Investing Basics area. You can also learn all about brokerages and find one that's right for you in our Broker Center.

Longtime contributor Selena Maranjian owns no shares of companies mentioned in this article.