What was something you wished you knew before investing in non-Singapore stocks?

In my case, it would be the US stocks in general. I wished i knew that good quality companies listed in the US may not be cheap in terms of valuation, and that valuation principles have to change depending on the type of business model of the company. I wished I knew that P/E and P/S wasn't an accurate valuation metric anymorefor some of the companies that I have come across. I wish I knew earlier that it pays to pay up for a quality company, even when valuation might be on the high side, because valuation is temporary. If the company is of good quality and can grow even further, it can compensate for the higher valuation that you paid at the start, where the forward valuation will be much cheaper or reasonable, as the company grew even more. Hope it helps!