A Card Only Matters If It's Going to Kill You
Magic is a complicated game. You can make it less complicated by not thinking about what cards do.
Panharmonicon? A neat card, does cool stuff, but it doesn't kill you.
Mentor of the Meek? Adds most of an Opt to all of your opponent's creatures, but it doesn't kill you.
Exquisite Blood? Part of an A+B combo with Sanguine Bond, but until then, it doesn't kill you.
A card that generates excessive value is a card that will kill you.
This is things that are generally going to statically two for one on a resource for you. Smothering Tithe, and Consecrated Sphinx are good examples of this. Rhystic Study is not. I have opinions on this, but that's for later.
Craterhoof Behemoth generates excessive value because you're making a dumb amount of power. Even then, it might not be enough to kill you.
It's okay to ignore cards that aren't going to kill you.
The common understanding in Commander is that 1 for 1 removal is bad, because it puts you down a card compared to your opponents. If you're killing cards that don't matter, that's true! However, we're only going to worry about cards that kill us.
It means we can leave up the one to three mana in the midgame for instant speed interaction, because we only care about cards that are going to kill us.
Sometimes, a card will get played that we know isn't going to kill us now, but will kill us later. That card is going to kill you. It's okay to think about it.