Getting stuck is part of the puzzle experience. You've loaded your tray with five mismatched tiles, and you can't see the pairs you need anywhere on the top layer. Panic sets in.
The first rule: don't randomly click. Take a breath and trace the layers. Sometimes, sacrificing a slot to uncover a buried tile is the only way forward. If you have a 'Shuffle' or 'Undo' power-up (if the game provides them), use them strategically—not when you are merely frustrated, but when you have mathematically proven there are no moves left on the visible layer.