Problem with my Warrior

I am some what confused and maybe someone could help.I have a lvl 20 W/M and I am farming somewhere outside LA.The problem is,my health,it will go from 300 + down to 1 in the blink of an eye.This happens after fighting or even when I am just standing there going through my inventory,sometimes i even die.I am not under any type of spell,chant or anything like that and I am not lagging at all,it just seems to happen for no reason at all,and it just doesn't happen when I farm.It doesn't always happen but every time it does I can find no reason why it happens.Can someone help,not sure what to think.
Thanks
S_S

A solo lvl 20 Warrior outside of LA trying to farm should have little problem in NM. Unless, you have Titan quests active, or are in HM solo.

If none of these are the case, then maybe you're getting attacked w/o you noticing it. Or maybe a vampiric weapon and a random shot is the culprit.

Too many variables to comb through without specifics.

1) Farming what? - need specific monster groups, zone, HM/NM, etc.
2) Build you are using
3) Armor you are using, including runes and insignias
4) Are you sure there aren't monsters near you when the health drop?
5) Are you sure you aren't lagging?
6) I bet you are using Defy Pain and/or Endure Pain

You've got either Endure Pain or Defy Pain on you and it is expiring.

1)Farming the bird people out side of LA in NM (for feathers)
2) Build:Sprint,Endure Pain,Defy Pain,You move like a Dwarf,Counterattack,Protector's Strike,Mighty Blow,Body Blow.
3)armor:Radiant Primeval helm of major Strength
Survivor Primeval cuirass of major vigor
Radiant Primeval gauntles of attunement
Radiant primeval leggings of attunement
Radiant primeval boots of attunement
4)This happens when all monsters are dead or far away from me
5)Could be a lag but the only thing that seems to act like a lag is my health bar,the rest of the game seems to be real smooth acting.
6) Yes I am using both,but I can't say that that isn't causing it,never really checked that out before,i'll change the two skills for something else and see if things change.
I will get back to you and let you know
Thanks
S_S

As said by others, it's probably Endure Pain and Defy Pain ending. When they end, you lose the health they gave you when you were fighting. I assume you have 15 points on strength (seeing the major rune), so Endure Pain gives you 300 more HP for 18 seconds, Defy Pain gives you 300 more health for 20 seconds.

After that time has passed, you will lose 600 hp, so you may check out how much health you have after the battle is finished, and if you are lower than 600, maybe recast Defy Pain if you have enough adrenaline, or bring some skills to heal you up over 600 HP.

My best bet is Endure/Defy is running out.

Also when you health boost skills ends and your at 1 of 500 health. Don't let it fool you, You really have -100 of 500 and if you use ANY skill you die instantly.

This mostly happens to monks and symbiosis, your max health can be boosted 1500+ but as soon as symbiosis dies you basically take over 600 damage. Which is fine if the monk is anywhere over 600 health but anything below that is danger zone.

This can be countered by simply not bringing the health boost skills without a healer. If you don't have a healer and you boost your health, when the skills ends you 'take damage' for each extra health you gained.

The reason why you take die when using any skill (defy pain, sprint, endure pain) at negative health, the game thinks your at 0 health and the game won't do anything unless you the player does something. If you want to still use your bar just wait until the negative health goes away with auto-regeneration.

Yup,
All of you are right,It was endure and defy pain doing it.I don't know why I didn't see it before,now I feel dumb.I should have known.I will just have to be careful and maybe bring a heal skill with me.
Thanks to all for the help!!
S_S

You will have 1 health when they end if you took enough damage while they were active. You will not die when they end though. The only way you will die if if you take a hit or have degen on you.... or if you try to heal. I'll make up some numbers to demonstrate the healing effect that would kill you.

500/500 health for starters
+300 from Endure Pain means you jump to 800/800
You take 600 damage while Endure Pain is up, dropping you to 200/800
Endure Pain ends, dropping you to -100/500, which displays as 1/500

Now, if your heal only provides 80 health, it would jump you to -20/500, which is dead.... you die from that. If your heal provides 100 health, you jump to 0/500.... again, dead. However, if you heal for 101 or more, you end up with a positive health value and still live. If you are not fighting, and wait, the natural health regen will eventually heal you without worrying about dying.

I'd also suggest changing your build. You have NF and GW:EN skills available, yet aren't taking some of the ones that would benefit you... like Lion's Comfort. And hammer may not be the best weapon, as an axe or sword would give you the use of a shield for more defense and health. Won't discuss it more here, but NM farming is a waste of time generally. Feathers drop there in piles of 7 in NM, but in HM they drop in piles of 19-21. Three times the feathers, plus chances for tomes is definitely a better reason to use HM.

Endure and defy pain?

Dude you were a walking corpse O_o

Fixed it for you.