Be confident, yet not boastful.

要有自信，当然不要夸夸其谈。

youdao

Prudent man, not boastful, others friendly and sincere.

为人稳健，不自诩，待人友善、诚恳。

youdao

I'm not being boastful.

我不是在自夸。

《柯林斯英汉双解大词典》

"He was terribly proud of what he did but was not boastful, " his son John told The Associated Press.

WSJ: US WWII veteran who captured Japan's Tojo dies

Mr Reiner is not a boastful figure.

ECONOMIST: American democracy

But he's not particularly loud and boastful.

CNN: STORY HIGHLIGHTS