>One of the hardest concepts for investors is the notion that keeping a share of stock is the same as buying that share of stock every day, since by keeping it, every day you are making the decision that that share of stock is more valuable than what the proceeds of selling it can purchase, which. except for the transaction cost, is exactly what you do when you buy it.

I don’t agree with this. Keeping a stock already purchased previously is not the same as buying a stock now. To demonstrate why take this hypothetical investing example; If I buy a stock and it goes up 100% then I have a very different view about holding that stock than another investor who is thinking of buying it today after it has already had this 100% move. Amongst other factors (1) I have a huge buffer against market retractions, and (2) I may be enjoying a great dividend rate that I got when I purchased the stock. Neither of which a new investor getting in today would enjoy.

The second part of your point; "...since by keeping it, every day you are making the decision that that share of stock is more valuable than what the proceeds of selling it can purchase..." is correct. When keeping a stock I am deciding that it is better for my money to stay invested in it than out of it doing something else. This statement is correct but it does not follow that keeping is the same as buying today. Keeping is the same as deciding it is better than some alternative use of the money.