Celebrate the lucky friend who bought his first stock within the last couple of months, and then watched it double in a day, and who knows that it can be worth a lot more. Is it already time to sell his MVIS, or buy more, or what? What’s happening here? Welcome to investing. Answers are always easy, in retrospect. Decisions are always made in ignorance – almost.

If you’re reading this anytime after market open on February 24, 2014 you already know what happened to MVIS. As I type it is Sunday night after a busy work weekend. My business has been so swamped that my Saturday morning posts were moved to Saturday night and kept sliding until Sunday. Maybe I should raise my rates. (Yes, Peter and others, I’m considering it.) During a break this afternoon I talked to a friend, a novice investor. His question: “What should I do? Sell? Or should I buy more?” The words of my reply were probably no more useful than the shrug that preceded them. I wasn’t dodging the question. I was just being honest. No one knows, but a lot of people will be happy to accept your money in return for strong declarative statements that deliver the voice of authority. We humans like thinking there’s an answer, even when we know there isn’t one.

I am not a novice investor. I may be an amateur, but I have almost 40 years of experience investing in stocks. A lot of examples have rolled past my eyes.

Let’s start with conventional wisdom. If you make more than 10% after taxes and commissions you can sell and proclaim yourself above average. On average, the stock markets return something in that range, sometimes higher, sometimes lower. If you made 10% in a day, and did that once per year, you’d double your money every seven years and not spend much time investing. The trick is picking the right day and stock, and then thinking you can do that every year forever.

A typical conservative approach. Sell when you’ve made 20% (or whatever percentage works for you). Buy back after a pull-back. Reasonable. Do it right and ratchet your investments up. Do that with MVIS last week and miss out on the next 80%, but profit is profit and congratulate yourself on the 20%. The trick is doing it consistently, and decided how long to wait for that rise. Days are easy. Decades may be too long.

A less conservative approach. Wait for the stock to drop 20% and then sell. That may mean selling right after buying if your stock is caught in a downdraft. But is also may mean selling after a stock has risen hundreds of percent. I sold AOL after it dropped 50%, but first it rose from about $1 to about $80. I sold at about $40. (It is Sunday night and I don’t want to look up the exact numbers. See my book for details.)  The trick is finally making that decision to sell. The difference between selling AOL after a 50% drop versus a 20% drop was two or three years living expenses.

Greed. Hang on forever and fall into that motto of; “Bulls make money. Bears make money. Pigs get slaughtered.” Which sounds like a great line until you find out what happens to most male cattle in this world.

Investing isn’t just about making more, then more, then more. (Cautionary tales in good movies: Dick Tracy with Madonna singing “More”, and Key Largo with Humphrey Bogart’s character revealing Edward G. Robinson’s character obsession with More.)

Personal finance is personal. What do you need? What do you want? Why are you investing?

The younger the investor, the more time they have, the more chances they can take, the more they can benefit from patience. I’ve heard advice for twenty-somethings that ranged from; “Be risky because it might work and if it doesn’t you can recover.” to “Be as conservative as possible because compound interest will do amazing things for anyone with enough time.” Both pieces of advice are correct. Youth have more options, they usually don’t know it.

Investors with less time or money are more likely to ignore the conservative approach. Financial disaster is too close to ignore. Money issues aren’t abstractions. Making money anyway possible is an every day concern. It is easy to put everything on one investment, which is really just a bet. Lottery tickets sell. The other 8,000 stocks are easy to ignore in such circumstances; yet, diversification is the cheapest risk reducer available.

Most folks live between those two extremes. They have time, but not as many years as they would like. They have an income, but maybe not as much as they’d be comfortable with.

There is no one answer. I think the best answer is within each person. Buying and selling stocks is about arithmetic. Is the stock overpriced or underpriced? Find a way you think is appropriate for estimating a stock or company’s value and run those numbers. Growth, value, momentum, income all have criteria to work from. Investing is about enabling a life you want to live. How much money do you need for what and when? If you are chasing a 10% or 20% return, you’re chasing math. Why are you investing? To retire early? To make enough money to redefine a lifestyle? To pay off a specific debt? Now thyself is the most powerful investing advice.

A lot of advice can sound abstract, theoretical, and philosophical. Get real. With stocks that have extreme debates over their possible valuations, like $0 < $MVIS < $1200, draw a chart. Take your number of shares and multiply them by 0, the current price and several prices on the way through the high value, and then a few more. Daydream, but do it for real. If the stock goes to zero, what do you do? If the stock rises, it will take a lot of time to rise. What will you do when it is up 100%, or has only reached 50% of its estimate, or has exceeded your highest estimate? Do you already have enough for personal “success” if the business and the stock succeed?

In personal finance, numbers aren’t as important as actions. I’ve ridden enough waves that I know that I’ll sell about 20% when I can pay off a major financial goal (credit card debt, or mortgage, or retirement, or ?). After that, I’ll let it ride but I’ll be watching for when I’ve made a profit, made 100%, 200%, 300%, 400%. If I haven’t sold by 400%, then I’ll sell 20%-25%. And, eventually I may sell off 80% and leave the last 20% to ride. (I’ve almost been there more times than I can readily count, and each time I was distracted by life, not finance.)

If nothing else, it is fun to imagine such trades. I’ve also seen the other side, when phenomenal misfortune means every investment dropped simultaneously and stayed down for years. But, within the last month, AMSC, GERN, and MVIS have all shown signs of recoveries large enough for me to ponder when and what to sell. It is refreshing to be able to ask such questions again, even when I know the answer is, Not yet.