If you're 20, don't sweat the daily. As others have said, go into SPY or something similar and let it go. If your brokerage offers auto-investing, buy more on a weekly or monthly schedule until your funds run out.

If you have 20k right now at 20, you have plenty of time to research individual stocks and I'm sure you'll have much more money where you can take higher risks later on in life.

That said, if you haven't maxed it out, put it into a Roth IRA and max that bad boy out each year. As someone more than double your age, I really wish I had listened to that advice when I got it around 22. This will become your most valuable money over time since it's all yours. The downside is that you can't really withdraw it without penalties until you're in your 60's.

Of course, everyone's situation is different and you may want to talk to a financial advisor about your specifics.