In college, I did some very small investing, mostly just to learn. Fortunately, the year I started my post-college career is the same year they started our company 401k fund. All of my stock investing for the past 36 years has been though the 401k.
I am much more active with my 401k than many of my coworkers. Some of them literally don't ever touch it. They have a mix of company stock, and fidelity managed funds, and they just let it do its thing. We contribute every month through payroll deduction, and that's matched by the company.
So, for example, there were a number of years when our company stock would go up, and then down, and repeat. Or the whole 401k would trend up, then down. Some people did nothing. Their net was zero. I always went with the big trends. I have my money spread over about a dozen funds. They range from stocks to bonds to equities to mutuals, large cap to small cap, domestic to international. After a run up to a high point, I'd transition to the low risk, low loss funds. After the market tanks, I go all in on the high return funds.
Diversification is good. I'm not sure what the future of Facebook stock is, but assuming it's at a high (or all-time high) like most stocks are, this would be a good time to diversify. It would be like taking the profits from Facebook, and using it to buy other investments. Of course, it's sort of like the housing market - when your house is at peak selling price, so is anything you'd move into.
So the trick is to go into stocks or funds that have growth potential now. I have friends who are making lots of money from Tesla, but I think it's late to get into that game. As for me, I'm in conservative mode (since the week before the election). When the market cools off, I will get more aggressive.