The 3kHz to 8kHz range is arguably the most frustrating area for guitarists and mix engineers alike. This is the presence range, which gives your tone its brightness, clarity, and edge. Unfortunately, it is also home to harsh, fatiguing frequencies—often described as "ice-pick" harshness or annoying, ringing whistles.
When dealing with this range, you must act surgically. Instead of using broad EQ moves that kill the life of your tone, use a very narrow EQ band to "sweep" and hunt down the specific frequencies that are piercing your ears, and notch them out.
Finally, we have the "Air" or "Fizz" range, comprising everything from roughly 8kHz and above. While a little bit of high-end air can make a clean tone feel open, high-gain distortion inherently generates a massive amount of useless high-frequency fizz. Implementing a Low-Pass Filter (LPF) around 8kHz to 10kHz will cleanly chop off that unwanted, fatiguing static, leaving you with a focused, professional-sounding top end.