If you have to ask a third party how much to hold, then you should remain relatively diversified. How I invest is a personal decision and many would call it not the sanest manner to invest. I invest in my manner for my own personal purposes.
How you should invest, and what percentages is not something that anyone on a chat board should assist you with. That is something you need to work out for yourself, and if you are at this position as an investor, I would recommend holding at least 4 or 5 different investments, and probably most hold many more. I think with at least 4 or 5, then a 100% loss in one is a 20% loss over all, which most people (except those near retirement) can usually tolerate.
This said, maybe 10 stocks might be a better hold for you. I don't know.
One thing I do know, is that trading in and out of stocks usually materially hurts your portfolio performance. You need to buy at good buy in points, know what and why you are buying, have patience, hold and keep holding until it is time to hold no longer. And if what you are holding and in the portion you are holding makes you stressed out, then do something to destress like further diversification. I don't think you really need more than 5, but 10 is a manageable number as well when you run the math.
If your going to hold more than 10 then you might be better off with a well managed (low cost) mutual fund. Since you are here, I doubt you want the mutual fund. Others may tell you that 5 is way too little, and that even 10 is not enough. But as I run the math, each share with 5 is 20% and each share with 10 is 10%, a catastrophic failure is therefore tolerable holding these number of shares, and it is still few enough to beat the market if you make good long-term investments. If you make poor long-term choices however, at these numbers, then it is few enough shares for you to lose to the market.
So my rec (and I don't necessarily follow it, but for most people it is very aggressive, but still not insane) is hold 5 - 10 shares that you know very well, bought at excellent times, have patience with it, and this provides enough diversification to avoid losing the ship, while still allowing market beating returns without having to become a full-time investment researcher.
Caveat: Free opinion, and I don't necessarily follow it, as I don't necessarily consider myself to be "most people" although in the end I probably am "most people" just like most people are.
Tinker
