Unconscious Protection[Peach]

[Oerlaf]

Unconscious protection
1st level abjuration
Casting Time: 10 minutes
Components: V, S
Range: Self
Duration: Instantaneous

Upon casting this spell, you place on yourself a bit of protection even if you find yourself unaware of surroundings. When you fall unconscious for the first time in an adventuring day, you cannot fail death saving throws from any other source except failing your death saving throw due to the die roll until you regain at least 1 hit point.

A more simple variant of wording:
Upon casting this spell, you place on yourself a bit of protection even if you find yourself unaware of surroundings. When you fall unconscious for the first time in an adventuring day, you gain immunity to all damage until you regain at least 1 hit point.

[Potato_Priest]

Instead of this "in an adventuring day" mumbo jombo, you could give it a duration of 24 hours and the following stipulation:
If you cast this spell more than once in the same 24-hour period, the spell fails and has no effect every time after the first.

[Oerlaf]

I gave it the Instantaneous duration on purpose so it couldn't be affected with Dispel Magic.

[khadgar567]

Needs better explanation

[zeek0]

I gave it the Instantaneous duration on purpose so it couldn't be affected with Dispel Magic.

What motivated this choice? But even so, dispel magic can remove this effect - it removes any magic on the target, not just effects with with duration.

Edit: also, what happens if my character is making saving throws and the villain throws me into a lake of lava, or drops a building on my head?

[Oerlaf]

What motivated this choice? But even so, dispel magic can remove this effect - it removes any magic on the target, not just effects with with duration.

Edit: also, what happens if my character is making saving throws and the villain throws me into a lake of lava, or drops a building on my head?

Lava case: it is supposed to act like a Sleeping Beauty: while you are unconscious, you are hidden in the lava lake but you do not fail death saving throws because of the lava. If you succeed on three saves, you are conscious again. But I understood what you meant.

So here is a little rework of the spell
Unconscious Protection
1st level abjuration
Casting Time: 10 Minutes
Components: V, S
Range: Self
Duration: 24 Hours, or until discharged

For the duration of the spell you gain immunity to all damage while you are unconscious. The spell ends for you when you are no longer unconscious.