You can intensify these by quickening your breathing a little, or by tightening your shoulders slightly as if you are bracing to carry a load.
Get familiar with the muscle movements--often subtle ones--associated with strength.
Just as making the facial expressions of an emotion will heighten that feelings, engaging the muscle movements of strength will increase your experience of it.
Get in the habit of deliberately calling up a sense of strength--not to dominate anyone but to fuel your intentions. For example, bring to mind a sense of visceral, muscular willfulness to stimulate your brain stem to send norepinephrine and dopamine like a rising fountain up into the rest of your brain for arousal and drive.
Bring the limbic system into the action by focusing on how good it feels to be strong. You will be increasingly drawn to strength in the future.
Add the power of cortical language by commenting on the experience to yourself: "It is good to be strong."
Notice any beliefs that it is bad or wrong to be strong, and send them on their way with counter thoughts like,
"Strength helps me do good things."
"I have the right to be strong. "
When you experience strength--whether you evoked it deliberately or it just came to mind--consciously take it in so it deepens its traces in implicit memory and becomes a part of you.
Rick Hanson, Ph.D.