1/ In the start of 2016, I sold $MA to buy $AXP bc it had lost roughly 50% of its market cap after losing the $COST partnership, and also because I was infatuated with Buffett and $BRK.

$MA was trading at $85 & ~30 PE. $AXP was trading at ~$50 & 10 PE. I thought I was a genius.

2/ Compounding my error was that both $SQ and $PYPL IPO& #39;ed around the same time and was told by many people to buy those instead of $AXP.

I laughed at them for buying $PYPL ~$40 and a 40 PE and $SQ at $14 wasn& #39;t even profitable. They don& #39;t understand investing, I thought.

3/ Since then:

$SQ +1,280%
$PYPL +451%
$MA +250%
$AXP +45% (I sold at ~$95 a few years ago)

4/ Worst of all my only other holding was $AAPL at that time and I did this because I thought I needed to start "diversifying".

Apple is +302.8% since then.

5/ Expensive (but important) lessons to learn:

- Don& #39;t sell a wonderful business to buy something cheaper
- Don& #39;t assume something is expensive just bc it is trading at a high multiple
- Don& #39;t be infatuated with what your heroes own
- Don& #39;t diversify just to diversify