Many good near field monitors are considered "harsh" to the point of being irritating, but they serve a purpose. One of the most commonly used over the last 2 decades or so, are Yamaha NS10's, (Obsolete now, and still sought after) and if you talk to many mixing engineers from the last few decades, you will often get the response "yeah, I hate those things" yet at the same time they were considered a mandatory tool. I call it "harsh reality"
Sometimes you need to clearly hear and judge frequencies that require a monitor that doesn't sound "pretty".
If we benefited from "pretty" we would just use some 3-way home stereo speakers to monitor, get the results pretty and call it a day.
Well, that has its utility as well.......
IMO, the best tool is probably familiarity.
A/B references in your DAW session. Mix down a version, sandwich it between two reference tracks and pop it in your car. Listen for a few days. TAKE NOTES, tweak and revisit.
Rinse, repeat, lose faith, keep trying, believe it or not, the harder you try the harder it gets at times.
Then you go back to some old work you thought was pretty good and you realize you've gotten better by leaps.....
Yeah, I wouldn't be surprised to get some flak from the haters, debaters and "know it all's" on the monitor calibration comment, but that's OK. Its an opinion, I own it. And the question is pretty general. Calibrate what aspect? Levels? Frequency response? Location relative to the lava lamp?
These might be important details!