君はよく勉強した、そうでなければ失敗していただろう。

You worked hard, or you would have failed.

君(きみ)はよく勉強(べんきょう)した、そうでなければ失敗(しっぱい)していただろう。

Kimi wa yoku benkyōshita, sō denakereba shippaishiteita darou.

君 (きみ)

you; buddy; pal; monarch; ruler; sovereign; (one's) master

は (は)

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

良く (よく)

nicely; properly; well; skillfully; skilfully; frequently; often

勉強 (べんきょう)

study; diligence; discount; reduction

そう (そう)

so; really; seeming; appearing that; seeming that; looking like; having the appearance of

だ (だ)

be; is; indicates past or completed action; indicates light imperative

失敗 (しっぱい)

failure; mistake; blunder

Readings: クン、きみ、 -ぎみ

Meanings: mister, you, ruler, male name suffix

Readings: ベン、つと.める

Meanings: exertion, endeavour, encourage, strive, make effort, diligent

Readings: キョウ、ゴウ、つよ.い、つよ.まる、つよ.める、し.いる、こわ.い

Meaning: strong

Readings: シツ、うしな.う、う.せる

Meanings: lose, error, fault, disadvantage, loss

Readings: ハイ、やぶ.れる

Meanings: failure, defeat, reversal