Struggling

I once had someone say to me in regards to school, but it's easy for you, you're smart.
I said the same thing now as I've been repeating to myself the last little bit: it doesn't come naturally to me. I don't naturally have this amazing cognitive memory or amazing skills that allow me to knock a paper out of the park on the first try. I struggle. Sometimes a hell of a lot. It takes a lot of determination for me to get through a set of notes or write up a draft. And I make sacrifices to do it.
There's this popular diagram of what it takes to be a successful student the requires you choose two out of good grades, sleep and a social life, but it's no where near as simple as that.
I've received some bad marks recently, ones that definitely won't see me into next year, and I'm struggling to figure out what's even the point. I worked hard and got through the bullshit in the past because I had an end goal in sight: I needed to get into Carleton, I needed to get into second year.
Well now I'm here. What's next?
I'm certainly not happy. I'm stressed, I'm tired and I feel so close to giving up. I need to discern for myself what I what/need from this. At the moment, I honestly cannot imagine myself forking out another $18,000 to suffer through two more years of this.
Over the past few years, school became my thing because it fit into the slot I needed in life to propel myself and make it to the next goal, but now my goals don't pertain to school at all. I just want out and I just want to feel healthy and happy again.
But I'm not sure how that can align with working 20 hours a week and going to school for 25 and somehow studying for the rest of the hours in between.