A lot will depend on the sport and what type of student you were in high school. Football for instance is officially practicing or playing their sport for almost 6 months. The next few months is weight room and conditioning. Then spring practice. Then a couple months of weight room and conditioning and then it starts all over again. Many other sports are similar.
Yet, I know first hand of a number of student athletes who were able to pull off 4.0gpa semesters and graduate the academy in the top 10-20 of their class. Then again, these cadets have been combining a difficult academic schedule along with athletics for the last 4-6 years prior to even coming to the academy. So for them it was no big deal. They've already trained themselves how to manage their time for classes, studying, homework, training, playing, and conditioning. Along with some free time for their social life.
In another breath, I know some athletes who struggled in high school trying to keep their grades up. Especially during their sport season. I've seen many of these individuals struggle at the academy. Some pulled it off. Some quit their sport and just went full time academics. Some couldn't manage their time and wound up getting kicked out because of academics.
So the question shouldn't be what can others tell you about being a student athlete. You know how you did in high school. If you were able to excel at your sports, be one of the best players on your team, and still pull off a 3.9-4.0 gpa, then you'll probably do OK. If you think you had a difficult time in high school, then the level of difficulty is going to go up much more at the academy. Most teams have tutors and academic assistance who help the athletes out. But you're still the one who has to do the work. Between NCAA and Academy requirements, you have to be passing all your classes to remain eligible. If the academy puts you on academic probation, depending on the time of year of your sport, you may not be eligible to play until your grades have improved. Football players have the advantage of being one of the first sports of the year. They can usually get through 2/3 of the regular season before grades become an issue. Some basketball players aren't able to even start their season if their grades are too low.
So again; judge for yourself how you did in high school and then at least double the the difficulty level. This isn't a regular college where you can take underwater basket weaving or time your more difficult classes for the off season. Even if you're a history major, you're going to take numerous engineering and similar type classes. And the academy schedules that for you. Best of luck.