With great power comes great responsibility. They told you you should be mixing at consistent levels, and they were right. But what they probably never bothered to tell you, I guess because they assumed you already understood, was that working at a standard listening level does not mean you leave your control room level in one place.
If anything, it’s the opposite. The consistent listening level you’re trying to maintain is at the listening position. So when you start with your faders low, your control room volume is going to be dimed.
Just remember you’re sitting on a rocket ship. We aren’t blasting the levels to our speakers because we are playing loud, but precisely because we aren’t. And all that extra throw on the fader effectively eliminates the need to solo anything.
As you build up your mix, eating away at your available headroom, you’re going to increment down your control room volume, all the time maintaining a consistent listening level. And by the time you’re done, your control room should be set at a familiar position, and your mix should be hitting at the level you expect. Along the way, just remember to be careful, because with great power comes great responsibility.