A Vietnam Situation is akin to the Vietnam War in which the U.S. walked in expecting an easy victory and wound up spending years and lives in a costly war.
In slang a Vietnam situation is any sort of job or agreement one walks into and expects to be simple to complete but one finds out it will be quite time consuming and/or expensive.
Lately this slang has been synonymous with an Iraq Situation
Man, my grandmother wanted me to go under the house and see what was rattling around under there. I said 'Sure' I mean it was just a rattle. Turns out There's like fifty hornets nests down there and her sewage line has busted. We got a plumber out here and fourteen cans of pesticide. The whole thing is a Vietnam Situation.
Instead of saying, "fuck my life," when ALL of life can't be THAT bad, it is much more appropriate to use the phrase, "fuck my situation."
it makes a direct reference to a specific situation within a conversation noting that a particular event or series of linked event in one party's life are in fact terrible or awkward.
when you're walking to your car from your JUST established fuck buddy's apartment, with him and your other classmate who lives in the complex as he, says "good morning."