Slay the Spire is a really hard game because you rarely get immediate feedback on your decisions. As human beings, we thrive on rapid feedback loops and can very quickly learn to do a task when they are present. It takes an entirely different sort of thinking to look back and say "all those attack cards I took in Act 1 just ended clogging my deck in Act 3!" when the two situations may be an hour and a half or more apart.

Another really challenging aspect to StS is that the immediate feedback you do get may be entirely unhelpful or even counterproductive. Taking all those attack cards in Act 1 can make your deck feel a lot more powerful... in Act 1. But essentially you've sacrificed the long-term viability of your deck for short term strength.