Never leave your paint brushes standing point down in your water container for long periods (well, not at all really), the bristles will bend and the brush will look like a hockey stick, you try painting with a hockey stick! If you do have the misfortune not too follow this advice and you do end up with a hockey stick you can sometimes straighten them out by using gouache or soap and cover the bristles and straighten out between fore finger and thumb and let it dry and, hey, presto, no hockey stickā€¦..hopefully!