tl;dr:
In a word, the more investment decisions I have to make, the more likely the distribution of my investments will spread on the return surface randomly.
Once I decide that I should hold my investment forever (forever ~= lifetime), I can settle the 3 trading questions once for all:
- What to buy? ->The Market - Because it’s the only investment vehicle that may last for my lifetime.
- When to buy?-> Whenever I have cash available for investing.
- When to sell? ->Never.