You absolutely have a point if coming from caressing the ball too much, trying to control the swing and ball speed instead of getting control over the shape and placement via swinging free and fast. One shall kind of unlock swinging faster, hitting faster, and that feels like going 100% or even above.
I just think it’s much more technical and habitual, and shall be practiced until it’s comfortable. Fear of missing of course might affect it, but before you got used to swinging faster on practice court, before your brain knows it is safe — you don’t just start hitting out of your shoes in matches. You swing fast in a match once you are pretty confident it’s the best thing you can deliver (like I absolutely cannot be consistent with tap-style second serves, I miss them all).
There’s absolutely a mental part to it, I can get tight and uncertain in a match, but it usually happens because my “swinging 100% on all shots” doesn’t work as I want it to work. But I still try to find the right intensity, because otherwise I loose to any decent player, can win some junkballing and attacking the net, but really lowers my level.
To sum up, ability to swing close to max speed on most balls comes from practice court. And it’s not like you hit screamers in practice — you learn to hit strong enough, safe enough balls in practice with full speed swing. That’s why I talk about rally balls rather than attacking and hitting hard on every ball. At least how it works for me, when it does