Japanese have traditionally excused boozy benders (ドンちゃん騒ぎの宴会) as the only opportunity repressed workers have to loosen up (打ち解ける) and tell the boss what they think.
どうでした? “have to = must” と解すると、いつまで経っても読めませんよ。同様の構文のセンテンスで短いものを一つ挙げておきます。
“Use every opportunity you have to practice English”
↑ <Is there anything you have to say?
これも、have to で解釈しない方が順当かと思いますが>
そうでしょうね。「云いたいことがなにかあるか」と読むのが普通しょうね。つまり、= Do you have anything to say? と解する。
次の例が参考になるかと思います。
Do you have any letters to write today? = Are there any letters you have to write today?
「ねばならない」という時の “have to” と “must” 間には微妙なニュアンスの差があるようですね。”Practical English Usage” (by Michael Swan) では、次のように説明されています。
If I say that you or I must do something, I probably mean that I feel it necessary. Have to is generally used to talk about obligations that come from “outside”. If I say that somebody has to do something, I probably mean that another person wants it done, or that there’s a law, a rule, an agreement, or something of the kind.
として、次の例を挙げています。
I must stop smoking. (I want to という気持ち)
You must try to get to work on time. (I want you to do という気持ち)
You have to go and see the boss. (He wants you to の気持ち)
Catholics have to go to church on Sundays. (Their religion tells them to という気持ち)