Sam Snead famously quipped that to grip the club with the proper amount of pressure, one should feel as if they're holding onto a baby bird: grip the club firmly enough that it can't fly away, but not so firmly that you crush the thing.
Less famously, Ben Hogan said "what Sam Snead didn't tell you is that the baby bird is a hawk."
If you had to guess whether grip pressures among amateur golfers were too tight or too loose, I imagine most people would guess they're too tight. It's common advice to "grip the club loosely" or "lightly" or "decrease grip pressure."
If you guessed that most amateurs grip the club too tight, you couldn't be more wrong. Most amateurs grip the club far too loosely.
Studies have been conducted on PGA Tour players and average amateurs. What they found was that the average PGA Tour player has the capacity to grip a club more than two times as firmly as the average amateur. So let's say a PGA Tour player says he grips the club at a "3 or a 4" on a scale of 1-10. The average amateur is only capable of gripping the club to a 4 or a 5, so that makes his grip pressure anywhere from a 6 to a 10 if you extrapolate the scale! Everyone's "3 to 4" is not the same. (There's another study I remember vividly, but I'll add that in a second comment.)
One thing amateurs do tend to get a bit "firm" with is in their wrists and forearms. What skilled golfers have learned to do is have relatively soft wrists, forearms, elbows, and biceps/triceps, and shoulders with a firm grip. The grip is primarily in the fingers and part of the palm muscles. The "firmness" stops at your wrist.
It's tough to practice the sensation - frankly, a PGA Tour player develops grip strength largely by hitting a few thousand balls per week. But if you'd like, go ahead and grip a club. Grip it FIRMLY. Now move your arms, wrists, etc. about - waving the clubhead around in the air - and try to feel as loose in your arms, shoulders, and wrists as possible while still maintaining firm pressure on the grip.
Grip the club firmly, people. If you're white knuckling it you may be in the minority and you may need to back off, but odds are you aren't.