There is a lot of talk about investments / trading on this thread so I thought I'd drop some of my thoughts and experiences here.
1) You can be right and still lose significant amounts of money. I've lost many thousands myself on something that I was eventually right about, timing is key - and it doesn't do to dwell on any decision - whether because you lost or could have made more. Sure, if I'd just invested my pocket money in bitcoin when I first mined it in 2012 I'd be retired already - but I didn't - shit happens.
2) If you are attaching emotion to your positions you're doing it wrong. This is a huge point, not one I've personally mastered - which is why I don't play with stocks anymore.
3) The whole cycle of emotions surrounding markets is explained brilliantly by George Soros in 'The Alchemy of Finance'. This is an excellent read. It's interesting and illuminating that Soros was a student of Philosophy and not strictly mathematics or business.
In my own experience there are two layers to markets - what actually is and what people think is or will be; usually the latter is much more powerful in terms of short term positions. One of Soros's points is that the two interact and influence the other eventually.