It really depends on your appetite for risk. I think I have some irregularities in the reward centre of my brain (read: I have always enjoyed gambling, although these days I tend towards well researched positive sum investments rather than whacking my salary on England to beat Scotland at 1.20 odds then cry as they happily draw 0-0).
Bearing in mind my disregard for risk, I invest in only a few shares at once, sometimes just 1 share.
I feel like diversifying is just lowering your chances of outperformance. To me having a widely diversified portfolio is like putting a bet on every outcome on a roulette wheel - you are guaranteed not to outperform.
Now if you back a small number of companies you are convinced will succeed, then you could be the next Bezos or Buffet or you could have terrible performance, but you only have yourself to blame for that.
No need for bemused replies, I am aware of how unpopular my opinion is, but I thought I’d share it for balance (can’t just have a thread of everyone saying how diversified they are)