You can definitely relax and continue to work to the best of your ability in future classes! Small anecdotal story… While there were ~30 or so students with unweighted 4.0s in my S25’s graduating class, he was not one of them. Of the UW 4.0 students, many did not take the most challenging classes. My S25 is very academically motivated, and has a close knit group of friends that are also academically motivated and talented. Of his close group, all but one had just shy of an UW 4.0. Most had 1 semester of 1 class that, just like you, something happened that caused their grade to slip. My S25 tested out of a class, and got a B on the test-out, which he decided it was worth taking because (long story short), it allowed him to have the prerequisites completed for an accelerated program he really wanted to participate in. It counted as a full credit (equiv of 2 semesters) of a B in that class on his GPA. He still got into a top 20 school! His friends also got into selective schools they were happy about. The UW 4.0 isn’t everything, and you still have plenty of time to work hard, pursue your interests, and aim for whatever schools you decide are a good fit for you when the time comes.