"I haven't shuffled enough, that's why this card keeps reappearing."
"There's too many reversals for this to really be accurate."
"I really need to learn to shuffle better, a card just flew out from the deck mid-way through. Now I can't possibly draw it or it's a biased reading in some way."
Here's the thing: in Tarot, there aren't really mistakes.
I'm not saying you can't give a bad reading. And not everyone's going to agree with me - I remember Dan Pelletier's "The Process" saying that once a card flies out of a deck during shuffling, "you've lost all credibility with your sitter," and I can understand exactly why he'd say so.
But I also remember The Devil practically shooting out from my hand during one shuffling. And I proceeded to lay it on the table, and ask if addiction had recently come into play for my sitter. As it turned out, her son was in prison for some of the things he'd done while on drugs. I pay attention to the cards that shoot out of my hand as additions to the reading now, and it never fails.
Repeating cards? Those are a capital-M Message for you, one you need to really grasp the meaning of when they show up. They'll haunt you across multiple decks until you really figure it out. Too many reversals? Maybe see reversals in a different light for this reading - as cards that are blocked/scattered energy, or energies you need to pay attention to.
Ask three Tarot readers and get five different answers. But the important thing here is that Tarot reflects what's going on in the world, and inside you, so it's a beautifully adaptable tool to whatever might happen. What's important is really your reaction, the connections you make. Your mistakes might tell you more about your question than a reading that's perfect, smooth sailing.
Agree? Disagree? I'd love to hear your personal interpretation of events like these in the comments!