How does ないと signify "must" in Japanese sometimes?


So my language resources gave me this sentence, in many forms and I still cant
understand where "must" comes from or the need to in the Japanese. It's
frequent, and I'm assuming a grammar phrase with no literal translation, but
mega confusing.

> そろそろ恐怖心に立ち向かわないと行けないね。

Translated as "It's time for me to face my fears."

In this particular sentence, it's the added 行けない at the end that confuses the
hell out of me, as my head is interpreting it as "must not".

More generally it's the use of these ないと and 行けない being paired I've seen used
a lot which confuses me, as I only associate it with a negation as nai general
meaning/use.

Thanks




First, yes, 〜ないといけない is a grammatical phrase, usually translated as "must" or
"have to". Correspondingly, it will usually be written in hiragana rather than
kanji.

Second, your confusion is totally natural; I think a lot of Japanese learners
will come across constructions with a couple of negatives and a conditional in
the mix and wonder how to parse it... But, there is some logic to this
expression, and you can break it down a bit if you must for the sake of
understanding it. The two things to look at are:

1) 〜ないと means "If (I) don't 〜", usually with a greater sense of
importance/associated repercussions than its grammatical siblings なければ or
なかったら.

2) While いけない can indeed mean "must not", it can (quite relatedly) mean
something like "it's no good".

Therefore, perhaps you might prefer to unpick the complete phrase ないといけない as
meaning "If I don't do it, it'll be no good - so logically, I must do it".

Hopefully, as you see/use the phrase more, it'll just click into place as its
plainer translation of "must" or "have to", but that sort of explanation might
help in the meantime.

