Always clean your brushes. Be kind to your tools. If you paint every day, it's a good idea, at the end of your painting day,  to clean all the brushes you used that day. I use a gentle soap and gently scrub all the paint out of my brushes. Rinse in cool water, shape the brush back to it's original shape and then let air dry flat. When all the brushes are clean and laying flat, I go back and  add a touch of soap to the chisel edge of my flat, round and liner brushes. No need to add soap to any scruffy brush or dry brushing brush. Let dry overnight, organize your brushes, before you begin painting again.