Training
Discipline
noun, verbal noun
When you forge and temper yourself, you're probably training your body or trying to discipline yourself to be physically and mentally tougher.
鍛錬 once described forging metal, but now it's usually about strengthening yourself. Think about how you push yourself again and again, like a blacksmith pounding hot iron, to mold your mind, body, and abilities into something stronger!! That's 鍛錬.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
発音が一晩で上手くなる人なんていません。発音を上達させるには、継続的かつ正しい鍛錬が必要です。
Nobody can get perfect pronunciation overnight. To improve your pronunciation you need continuous and proper training.