What effects does the foreshadowing in fair laurence’s warning to romeo have

These violent delights have violent ends,/ And in their triumph die, like fire and powder/ Which as they kiss consume." He foreshadows the death of Romeo and Juliet.
Friar Laurence tells Romeo that he should go slow, because those that run stumble. He says that Juliet and him should go slow, because they fell for each other so fast, they ought to run into a problem.. and they did.
Early on, before the Friar actually marries Romeo and Juliet, Romeo has to ask Friar Laurence to merry them. Friar Laurence warns him (I have no direct quote) that those who run too quickly trip and fall, or something along those lines. He means not to act too quickly- they had only just met- and doing so may result in disaster, which, sadly, it does.