If that's losing it, I better never stream myself playing Dark Souls, lol.
Don't worry Jeff, you'll get that fucker next time.
The thing about Crystal Sage is that yes, it is an easy boss in the grand scheme of things, but it is deceptively so.
Although it's weak to attacks, and doesn't smash you as hard as the big armored dudes you usually face, it's very easy to get ganked by a swarm of projectiles from off screen.
So basically, the fact that it is so "weak" on a 1 on 1 level, lulls you into a sense of security that is fatal, when his clones come up and start spamming shit from all angles, and at that point it's easy to get staggered to death with even one false roll.
People who call it easy, are probably more familiar with a shieldless build and are used to moving around swiftly, dodging multiple attacks.
I know that's the type of "skill" that helped me in that fight (though admittedly I didn't have much trouble, but exactly for that reason).
In short, spatial awareness is everything with that boss fight, and you sort of have to predict/assume, that a projectile is coming your way, even if can't see it.
Which makes it possibly more tricky than a 1 on 1 big dude sparring match, depending on your play style.
So yeah, don't feel too bad about it.