Besides the relevance of learning about theory I believe it is important to create blocks of time in which we allow ourselves to explore out of our comfort zone. This applies to any area where we would like to improve: drawing, painting, creating music, dancing, and of course, designing too is a result of practice.
This week I re-encountered this awesome book that has been in my shelf for a while: Creative Workshop: 80 Challenges to Sharpen Your Design Skills (also available for Kindle). The book presents a compilation of exercises that range from creating a typeface to designing a paper robot, and all of them within a time set period.
Also, it is not strange to be surprised by tasks that are unfamiliar to us, tasks that present a problem that needs to be resolved as soon as possible. In moments of crisis we might better access our intuition as designers. Even though intuition is something that cannot be teached, we can become more intuitive by frequently solving wildly divergent design problems.