You can, just be doing some mental exercises. Here are some scientifically proven workouts to help build those character traits, courtesy of  Women’s Health magazine.

• Boost your assertiveness, nod your head. Researchers at Ohio State University found that when we nod or shake our head, we think we’re communicating with others, and we are – but we’re also communicating with ourselves. Nodding makes us feel more strongly about our opinions. So, a day or two before you have to lead a meeting or talk to a teacher about a problem your child’s having, lock yourself in a room alone, and practice what you want to say while nodding your head vigorously. It’ll help you be clearer, firmer, and more coherent when it comes time to actually make your speech. And during the speech, nod occasionally.
  
  
• Become a more persuasive speaker by exercising. Researchers measured how smoothly and easily people spoke before and after they walked on a treadmill. In other words, did they sound confident and like they knew what they were talking about. Or did they hem-and-haw, and struggle for the right words. It turns out that all the volunteers who exercised for 30 minutes scored twice as high on verbal tests after their workout. If you want to try this yourself, you need to jump on the treadmill just before you need to sound smart. The effect lasts 20 to 50 minutes, but the more you do it, the longer the effect will last.
  

To recap, boost your assertiveness by nodding your head, and be a more persuasive speaker by exercising. Try those, tell me how they work for you at 866-865-TESH.