Well, conversely, is there anything to lose by doing it now...?
If the answer to that is no, and it provides some satisfaction for yourself to pass it, there's no reason not to.
Also, don't underestimate the benefit of hindsight and maturity of character - as a young person, for most their approach to learning was fairly different to how they may approach it as an adult. Since as a school aged student you had no experience of anything but the education system, it's not unusual for them to feel some sense of "burnout" by that stage - however with experience of life comparatively and greater self discipline learned through trial and error as an adult, it's very possible you'll take things more seriously and approach the subject in a different manner.
This could well lead to you doing much better than you did before - a C is certainly plausible, and above that is very possible.