I have read many 'stories' (some are so ill written I can't even bare to call them stories) online written by teens (many on Wattpad) and many of the stories are just packed with profanity. I personally think that profanity is okay, but there is a limit. Many of us swear (or at least think of swearing) when we are so over come with emotion or something over whelming has happened. But many of the stories I have read on just Wattpad use profanity kind of in this way:
I just &!*$ loved his so #&@*! much! When I first saw him I was just went Holy #@&!

I was raised in a conservative home so personally in my own writing I have a rule that I force myself to follow. Replace any curse words with a different word unless there is no alternative. As I wrote up above, I think profanity is okay with limits. I'll give you an example that my dad gave me. A soldier (soldiers being known for 'colorful' language) will not say, "Dang it! That son of a biscuit shot me my fudging leg!" He is going to use the neon colors of the language color box. So wherever a swear word seems appropriate I think should definitely be used. So for myself I try to avoid using swear words, I think that they can be avoided and be replaced with better words.
If you replace every curse word with a different word you'll maybe find yourself becoming more articulate. So I encourage you to try and replace curse words; I tend to replace everything with food (but not when I write... I can't see my characters calling someone a son of a biscuit).

Here's an article about novels with swearing and here's another one, that is actually written by an author (I always like to get fellow writer's perspective on writing, it makes it more relatable).