I'll burn that bridge when I get to it.
A combination of "I'll cross that bridge when I get to it." and the old addage, "don't burn your bridges". Meaning that you haven't yet arrived at a life obstacle, but you're sure you'll mess it up when you do.
"Hey man, did you figure out how to break the news to Kim that she's got herpes?"
"Nah, I'll burn that bridge when I get to it."
"Nah, I'll burn that bridge when I get to it."
I'll burn that bridge when I get there
Having clear vision of a unavoidable and bad decision on the horizon and agreeing to wait for the catastrophe rather than rush it.
"When grandma finds out I'm living with a woman shes gonna know I'm a lesbian, but I'll burn that bridge when I get there"