If there's one thing artists need to keep in mind is that they should never stop learning. It is easy to fall into a set mindset. Once we have learned something we assume that it is learned. And while that is somewhat true, all skills can be developed, modified and refreshed. Repeating the same thing over and over again can lead to stagnation of your art and your motivation. Nobody wants that! You want your art and your mind to be fresh and exciting! The best way to combat this is to learn and try new things.
What are some ways to learn new things?
There are plenty!
1. Take a class
Maybe you have been sculpting for 15 years and are fairly certain you know everything there is to know about sculpting (you don't, by the way). There are tons of online courses, many of which are free or cheap, or you can try to find a class at a local art school. Either way, many times these classes can show you techniques and tools that you may be unfamiliar with. Everyone has a slightly different process, so being taught by others can definitely broaden your skill pool.
2. Revisit failed attempts
Sometimes when you are learning a new skill everyone tells you to try it a certain way. But no matter how hard you try it just doesn't work out. So you develop a new way to do it and it works so well you never look back. Good for you! That's awesome! But you should totally look back. Sometimes a technique that seems simple to the established artisan can be rather difficult for the beginner, but can still be a valuable technique. Go back to things that didn't work out when you were a fledgling and try to do it that way.
3. Do something a little differently
Do you have a routine? You pick up your pencil and map out a sketch, starting with a figure and then mapping out the background. Well try figuring out the background first this time. It's easy to get comfortable with the way we do things, but it's great sometimes to try something new. Go on youtube and watch the way other artists do what you do and then try it for yourself.