The Strength card in the tarot represents a calm, inner strength and beauty. The fortitude to face spiritual tasks and trials. The ability to face a problem with hope and optimism. The emphasis is on inner, flowing strength rather than a display of brute strength.
The lion is meant to represent our fears and emotions that we need to tame before going on to explore our inner, more spiritual selves. The taming of the lion refers to the taming of our fears that control us, replacing them instead with strength and grace.