Quick Tip: How To Eliminate Hidden Selections in Photoshop
Sometimes when you're working in Photoshop, you'll find yourself unable to perform an action such as trying to paint or clone on the canvas. You'll look over to your Layers Panel to see you're on the correct Layer, but Photoshop still won't allow you paint onto the canvas. That's probably because you made a small selection somewhere by mistake or your forgot about it, and it's preventing from working outside that selection. Sometimes it can be Photoshop that is misbehaving; but in most cases, for me, its due to hidden selections. Simply press CMD+D to rid your document of hidden selections.