Strength has two primary aspects:
energy & determination.
You can intensity these by quickening your breathing a little, or by tightening your shoulders slightly.
Ge familiar with the muscle movement---often subtler ones--- associated with strength.
Just as making the facial expression of an emotion will heighten that feeling, 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 anybody or anything, but to fuel your intentions.
Involve the entire neuroaxis in order to power up your experience of strength. For example, bring to mind a sense of visceral, muscular willingness 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, so you will be increasingly drawn to strength.
Add the power of cortical language by commenting on the experience to yourself.
Add such a mantra to your language,
"I am feeling strong, It is good to feel strong."
When you are experiencing strength---whether you evoked it deliberately or it just came to mind---
take it in so it deepens its traces in conscious memory and becomes a part of you.
Buddhas Brain - Hanson