Make conscious effort to learn and to use a wide range of drawing styles.  It is up to a designer to be able to sketch any form or vision, and adapt his/her style to that and not expect a project to fit around what he/she is able to draw easily. A key ingredient of creative mindset is the enthusiasm for taking inspiration from a wide range of sources, and especially the readiness to seek inspiration from outside the professional field. This was me to push myself to try different styles. But I have to admit, I constantly made some changes on forms too along the way, old habit. The goal here is not to become a clone, but to learn new ways to communicate visually. Ultimately, everything  you learn will blend and be incorporated into your own personal style.