Not very helpful:
The Trinity: Try to Understand It and You’ll Lose Your Mind. Try to Deny It and You’ll LOSE YOUR SOUL! –mercifully anonymous but sadly widespread
Much better:
Nowhere else is a mistake more dangerous, or the search more laborious, or discovery more advantageous. –Augustine
Sweeeeet:
It is rashness to search too far into it. It is piety to believe it. It is life eternal to know it. And we can never have a full comprehension of it, till we come to enjoy it. –Bernard of Clairvaux