I don't have any sage words for you, just do your best.

You as a professional musician have to understand that you can't just go play your jazz.
あなたもプロのミュージシャンなら心得ておくんだね。自分のジャズをやっていればいいわけじゃないんだ。

You didn't have to quit because you didn't do anything wrong. 
That female supervisor was just mean to you for no reason, right?
君が悪いことしたわけじゃないんだから、君が辞める必要なかったのに。
何の理由もなく、あの女性上司が意地悪したんだろ？

I don't have any sage words for you, just do your best.
君への賢明なアドバイスは何もないが、ベストを尽くせばいい。

Of course, Tom, you don't have to help out if you don't want to. 
But just to keep the record straight, you volunteered.
トム、もちろん、嫌なら手伝わなくていいんだよ。でも、はっきりさせておくけど、君の方から志願したんだよ。