Absent a lot of surprises, stocks are relatively predictable over twenty years. As to whether they're going to be higher or lower in two to three years, you might as well flip a coin to decide.
The list of qualities (an investor should have) include patience, self-reliance, common sense, a tolerance for pain, open-mindedness, detachment, persistence, humility, flexibility, a willingness to do independent research, an equal willingness to admit mistakes, and the ability to ignore general panic.
If you're prepared to invest in a company, then you ought to be able to explain why in simple language that a fifth grader could understand, and quickly enough so the fifth grader won't get bored.
In the long run, a portfolio of well chosen stocks and/or equity mutual funds will always outperform a portfolio of bonds or a money-market account. In the long run, a portfolio of poorly chosen stocks won't outperform the money left under the mattress.
Thousands of experts study overbought indicators, oversold indicators,
head-and-shoulder patterns, put-call ratios, the Fed's policy on money supply, foreign investment, the movement of the constellations through the heavens, and the moss on oak trees, and they can't predict markets with any useful consistency, any more than the gizzard squeezers could tell the Roman emperors when the Huns would attack.