Like Shield. I'd probably set Shield to trigger automatic whenever my wizard would be hit and it would save him from taking damage, at least at lower levels when HP is low. I don't need a prompt at that point because casting Shield would save his life. I'm going to cast it every time because he has low HP. Later, I might turn it off or set it to prompt because he has more HP and I might not want to waste the slot.
This will use your spell slot. sometimes it's better to take the hit
