I would put in the work anyway to study for your final. Yes, numbers are looked at, but they aren't the end all be all for many people. To me it would be more concerning to see someone give up on something because they resigned themselves to not do well. Numbers say relatively little (to me at least) about ability/intelligence/capability. They also say absolutely nothing about effort and drive. You are interested in a career that is challenging and not always rewarding - drive to push yourself to work/study/improve even when you think you may not succeed is really important to your future in this field. People who will not be successful are not people who think they won't achieve their goals, they're people who stop because they think they won't achieve their goals.
I know this is a silly pep talk, and it feels like I peeled it off of one of those motivational posters with a kitten clinging to a tree on it. What I'm saying, though, is that I have never looked back on something with regret when I know I put absolutely all of my effort into it. I do, however, feel regret when I think about all of the things that I failed at because I refused to try or to put in due diligence.
When you have a choice, choose to put in the effort that will make you proud of yourself at the end of the day, regardless of the outcome.