Most solitaire losses aren't bad luck. They're the same mistakes, game after game. Open a game, play a few rounds with these in mind, and see what you start noticing.
Mistake 1: Emptying a column with no King to fill it
An empty tableau column is only useful if you have a King to put there. Without one, it's dead space.
Before you clear the last card from a column, ask which King you're planning to drop in. No answer? Find a different move. A blank column that sits there for several turns costs you flexibility without giving you anything back.
One exception: if clearing the column flips a face-down card, it's usually still worth doing. A revealed card opens options. An empty column waiting on a King mostly just sits there.
Mistake 2: Racing one suit ahead
Sending cards to the foundation feels like progress. It is, eventually. The trouble is doing it unevenly.
Say clubs are on 8 while hearts are still on 3. Every red 4, 5, 6, 7, and 8 you might need for tableau moves is now locked away. You've taken cards out of play for no good reason.
Try to keep all four piles within a rank or two of each other. If one suit is pulling ahead, hold off until the others catch up.
Mistake 3: Ignoring the deep columns
Some tableau columns have six cards buried face-down. Some have one. Every flip opens new moves, so the deep columns deserve your attention first — not the ones where everything is already visible.
The easy mistake is grabbing whatever move is available without asking what it uncovers. Two moves can both be legal. The one that flips a card in a heavy column is almost always better than the one that shuffles face-up cards around for no gain.
Mistake 4: Moving cards just because you can
This one is easy to miss because you feel like you're playing when you do it.
Moving a card that doesn't uncover anything, doesn't extend a useful sequence, and doesn't open a column is usually just shuffling. It can also block something you'll need a few turns later. Before moving a face-up card to another column, ask whether this actually does anything. If the honest answer is no, skip it.
Undo is there for exactly this situation. Try the move, see where it leads, take it back if it goes nowhere.
Mistake 5: Cycling through the stock on autopilot
Flipping from the stock feels like doing something when the tableau is stuck. But going through it quickly without really looking at each card is a habit that costs you.
Each card you draw is available once, right then, at the top of the waste pile. Flip past it without thinking and you've already forgotten it. Then a few turns later you're stuck waiting for it to come back around.
When you flip from the stock, actually stop. Can it go anywhere on the tableau? Even if the answer is no, knowing what's sitting in the waste pile stops it from catching you off guard later.
Mistake 6: Quitting before you're actually stuck
The board looks frozen. Nothing's moving. It's tempting to deal a new hand.
Positions that look stuck often aren't. A card still in the stock might unlock several moves when it surfaces. A face-down card near the bottom of a column might be the exact thing blocking you. Most players quit well before they've genuinely exhausted their options.
Before dealing a new hand, run through the stock once more and check every face-up card on the tableau. If you're still stuck, it might be one of the roughly one-in-five deals that can't be won. Usually, though, there's still something left.
Most of these mistakes are invisible until you lose a game you can trace back to a specific bad decision. Start a game, let yourself make them, and see which ones you recognise.