i don't quite understand this sentence's structure.

撞鬼，mindful 當然唔係 verb！
圖片參考：http://hk.yimg.com/i/icon/16/59.gif

呢句結構其實冇乜野，只係刪去左一部份o者。
全句主詞，好明顯，I decided not to go out 呢度已經明言，係 I。
前一句 mindful of X 雖然冇主詞，但其實呢個形容詞所講o既，係全句主詞o既心理狀態。全句 "mindful of X" 就係好似一「句」形容詞咁描寫緊主詞。原本全句係：
I was mindful of X.
依家因為兩句都係同一主詞，就省略主詞同 be，變成：
Mindful of X, I decided not to go out.

有時你見到一ｄ句子如：
Having picked up the bill, she went to a bank to pay it.
Struck by the ball, Tom fell unconscious.
呢ｄ叫 participle clause，都有ｄ類似。

It is because you are in the stage of very careful/mindful way for the tropical storm which may cause you bodily harm/dangerous.So, it's a verb.