You are recommending a SMR video for me?
Yes, I've seen it. like SMR a lot and agree strongly with
most of what he says, almost all. I generally agree with him on diversification also. But even SMR is quite diversified by my standards which take into account age, expensive, income sources, etc. This is why I say the right level of diversification will vary by individual. I've been under-diversified quite strongly since I started investing over 30 years ago and I like it that way. But I've never been 100% in any asset. I retired from fishing in Alaska precisely because I was extremely concentrated in one stock appreciating rapidly (over 70-90%) and I didn't want to sell
any of it and I didn't want to be on a fishing boat for over 3 months where I
couldn't sell if I wanted to. So I retired (permanently) and watched it like a hawk because I had so much on the line (millions).
Some diversification is a very good idea unless you want your life to be ruled by investing (and even then it has it's place). The question every investor needs to answer for themselves at any given point of their life is "How much"?