I am French, and I am looking for ideally a word or a short expression to express the situation where someone is about to do something that is going to put at danger/risk a goal/target. Let's say someone is stopping smoking. What do you call the moment he fights against himself not to take a cigarette. Or someone who is making a diet and is fighting not to take that delicious pizza... I'm sure you get the idea.
The first phrase that occurs to me for the person's emotional state is internal conflict.
The overall situation might be called a test of willpower.
You might call it the moment of truth:
a moment when a person or thing is put to the test
I'd call such a moment inner turmoil. Instead of turmoil, you could also use struggle or conflict. I also like chaos's internal.
I'm not sure turmoil or willpower or internal apply very well to the general case. This statement equally fits the question: "This bridge won't be open in time for Bastille day if we don't appropriate more funds by close of business today".
Today, in the above example, is do or die. It's make or break. It's a deadline and the engineering is giving the committee an ultimatum. All of these phrases apply to the situation. I'm not sure what the impact of your phrase is intended to have, but I think make or break fits very well, though it's colloquial.
I believe temptation, suggested by FumbleFingers here, deserves its own answer. Your protagonist is tempted to take the cigarette or the pizza, making the situation one of temptation.
In Catholic doctrine, a circumstance that puts one at risk of doing something wrong is called an "occasion of sin". The attractive acquantance who offers the abstainer a smoke, drink, sex, etc. is establishing that occasion of sin, which is, of course, to be assiduously avoided.