>>4220392Know how to work your way around yahoo answers and absolutely maximize your usage of online resources
Kahn Academy is really good, 3blue1brown has a good series on Calculus, nancypi/mathbff is also good
If you have the money, I recommend a chegg subscription, they seem to have everything, even explained.
Also always keep in mind your grade is not really a reflection of your intelligence, but of how much work you put in. Practice, practice, practice and it will pay off