他冷静自信地说。He spoke in a calm, assured voice.直视他人,自信地行走.Look others in the eye and walk with confidence.我想,他的意思是说他正在娴熟地 、 欢乐地 、 平静地和自信地滑雪.I believe he meant he was skiing skillfully, joyfully, peacefully, and confidently....

“自信地”的英语可以翻译为：assertorically ...