AP classes really aren't any much harder than regular classes, as far the material that's taught. The curriculum is basically the same as the regular class. It may move a little faster or go a bit more in-depth, but it's not like you'll be learning anything appreciably harder.
Many students actually find AP classes easier to do well in! For one thing, they're usually taught by the stronger teachers, who are good at explaining the material. Also, you're in class with the more serious students, so you don't have a bunch of goof-offs disrupting class all the time. You'll have classmates who know what's going on and can help you; and when you have group projects, you'll be paired with students who actually care about getting a good grade.
What makes AP classes "harder" is the amount of work involved. You'll generally have more reading, homework and special projects than you do in regular classes. If you're a disciplined and organized student who doesn't mind homework, then it shouldn't be a big deal. However, if you're the type of student who would rather amputate your own arm than spend and hour reading, then AP classes might not be for you.
There are many benefits to taking AP classes. They prepare you for the more rigorous classes you'll be taking in college. They also help you get IN to college. Colleges want students who have challenged themselves by taking the most advanced classes available to them... and for many colleges, the type of classes you've taken is more important than the grades you got. If your schools weights AP classes with extra points, that can boost your GPA and class rank, which will also help with college applications. And if you score high enough on your AP test, you can earn college credit for that class and skip having to take it again in college... which will save you time and money.
I would take as many AP classes as you think you can handle!