病気になってはじめて健康の大切さがわかりました。
- It was only after getting sick that I understood the importance of health.

病気になってはじめて健康の大切さがわかりました。 meaning: I realized the importance of health only after I became sick.

⚫︎This pattern means ...te hajimete, which translates to for the first time after... or not until.... ⚫︎It indicates that a certain realization, state, or action did not occur until a specific prior event took place. ⚫︎In this sentence, 病気になって (having become sick) is followed by はじめて, showing that the realization came strictly as a result of that experience. ⚫︎病気になってはじめて means for the first time after falling ill.

⚫︎This structure connects two nouns using the particle の to indicate possession, association, or a modifying relationship. ⚫︎健康の大切さ consists of the noun 健康 (health), the particle の, and the noun derived from an adjective 大切さ (importance). ⚫︎It literally means the importance of health. ⚫︎The particle の here links the modifying noun to the main noun it describes.

⚫︎The suffix さ can be attached to the stem of i-adjectives or na-adjectives to convert them into abstract nouns representing a degree or quality. ⚫︎大切 is a na-adjective meaning important. ⚫︎By changing 大切 to 大切さ, it becomes a noun meaning importance. ⚫︎This allows the concept to act as the direct object of the verb.

⚫︎The particle が marks the grammatical subject of a sentence or clause. ⚫︎In 健康の大切さがわかりました, 健康の大切さ is marked with が because it is the thing being understood. ⚫︎While English typically uses a direct object with to understand, Japanese grammar treats the target of comprehension with the subject marker が when using verbs like わかる.

⚫︎The verb わかる (to understand) is a Godan verb. ⚫︎In this sentence, it is conjugated into the polite past tense form わかりました. ⚫︎The stem changes to the i row sound わから + い becomes わかり, followed by the polite past auxiliary verb ました. ⚫︎This indicates a completed realization in the polite speech style.