There's a kind of tension for players who are concerned about playing well, and it's this: if you care a lot about victory and defeat, and you're grinding out lots of games to try and improve, you'll naturally start adopting patterns of play. Developing patterns is mostly good: save mental energy by formulating frameworks and strategies to follow, right? You had a great run with a specific card, so every time you see that card, you remember what synergies generally worked and try to replicate them.

But adopting patterns creates problems when you start to accept too many things as a given. For example, "thin decks can be good with certain cards" can easily become "always keep your deck thin". Or "This card combo is pretty strong" becomes "I see this combo is available, so I'll ignore other potential strategies".