How Protection Crystals Work
Most people buy a protection crystal the way they'd buy a smoke alarm. Set it up once, forget about it, assume it's working. Then something drains them anyway, a difficult phone call, a visit that left them exhausted, a week where nothing went wrong but they still ended up depleted, and they wonder if the crystal failed.
It didn't fail. It was never built to do the job you were asking of it.
An alarm tells you something's wrong after the fact.
A shield stops it from reaching you in the first place.
Most crystal protection, as it's usually practiced, functions like an alarm, a stone sitting quietly somewhere in your home, absorbing what it can, occasionally getting "full" and needing a cleanse.
That's genuinely useful. It's just not the same thing as actual protection, and treating it that way is where the disappointment creeps in.

A shield needs two things an alarm doesn't: placement, and renewal.
Placement means putting the stone where the draining thing actually enters your life, not just somewhere in the room. If it's a person, that might mean carrying it during the visit rather than leaving it on a shelf. If it's your inbox or your phone, that might mean keeping it near your desk rather than your bed. Protection has to sit between you and the thing, not just near you in general.
Renewal is the part people skip. A lock that's never checked eventually gets left unlatched by accident. A protection stone that's never re-set eventually becomes background furniture, present but not actually doing anything, because the intention behind it faded weeks ago even if the stone didn't move.
Matching the stone to the actual threat
Not every kind of draining is the same, so the right stone depends on what's actually getting through.

If it's people, specifically their moods, their opinions, their neediness, Black Tourmaline is the standard choice. It's blunt and effective, good for the friend who overshares their crisis onto you or the coworker who leaves every conversation feeling one-sided.
If it's your own overthinking, the loop that starts the second you're alone with your thoughts, Hematite is more useful than Black Tourmaline. It's grounding rather than blocking, better suited to protecting you from yourself than from other people.
If it's information overload, notifications, news, the sheer volume of input in a normal day, Smoky Quartz works well kept near whatever device is the worst offender.
If it's a specific relationship you're still tangled up in, even one that's technically over, Obsidian is built for cutting that particular kind of cord rather than general shielding.

Turning a shelf stone into an actual shield
Whatever you've got sitting on a shelf right now, protection crystal or not, here's how to make it actually functional instead of decorative.
Identify what's really draining you. Not vaguely, specifically. Name the person, the habit, the hour of the day it tends to hit.
Move the stone to intercept it. If it's a 6pm phone scroll that leaves you wired and anxious, the stone goes next to your phone charger, not your nightstand. If it's a particular relative, it goes in your pocket before you see them, not on a shelf they'll never walk past.
Set a renewal day. Weekly is enough. Pick up the stone, hold it for a few seconds, and consciously re-state what you're asking it to do. This is the step that turns it back into a shield instead of letting it quietly become furniture.
Notice, honestly, whether it's helping. Not in a mystical sense, in a practical one. Do you feel less depleted after the thing that used to wipe you out? If not, the placement is probably still wrong, not the stone.
Protection was never meant to be passive. The stone does some of the work. The rest is you actually putting it where the draining thing lives.