Why did Korra not use the Avatar state sooner in Book 3?

Question

Spoilers for Avatar: The Legend of Korra Season 1-3. below.

Korra became able to enter the Avatar state at the finale of Book 1, and we have seen her using it numerous times in Book 2 - even for cheating in a game with Tenzin's children. Even after the happenings of the series's finale, she is clearly capable to go in and out at will.

Still, she never tends to use it when she's in actual danger.

Not for a moment while she's fighting with Zaheer and co., though she and her friends are definitely in great danger. She even loses, without ever using it.

Later she and even her Avatar self is in much more direct and serious danger: being chained up, the Red Lotus want to poison her, and kill her in the avatar state, ending the cycle for good.
She just shakes her chains desperately. I find this really surprising, especially since, as demonstrated under the effect of the poison, she is clearly more than capable of escaping and defeating all the three remaining RL members in the avatar state. It seems had she do this sooner, she could have put an end to the fight much earlier, and never would've got poisoned. And (S04 spoiler)

before season 4, she never had any reason to fear going in the Avatar state. She had hallucinations only because of her poisoned body and fearful mind.

Right, the Avatar state is described as a tool for self-defense by Avatar Roku in TLA, but if avoiding being poisoned isn't self-defence, nothing is. It's also risky for the possibility of the cycle being broken, right, but that's what Zaheer was planning to do anyway. And various avatars used it many times for defending others (see e.g. Avatar Kyoshi separating an island from the continent, or Avatar Roku fighting a volcano to buy fleeing people time). Korra itself used it for things from energy-bending and soul-purifying (see S03E01) to cheating - why not for "really serious business"?

Why is Korra so reluctant to use the Avatar state for fighting?

Answer 1

There are a number of reasons as to why Korra is reluctant to use the Avatar state in book 3.

1. The Avatar is most vulnerable in the avatar state:

   As stated by Roku in The Last Airbender, the avatar state does provide significant power increase, but it is also when the Avatar is the most vulnerable. If the Avatar is killed while in the avatar state it breaks the cycle and the Avatar can no longer resurrect.

2. The avatar state leaves the Avatar physically exhausted afterwards:

   This was most prominently seen with Avatar Aang, who was always physically drained after coming out of the avatar state. When Korra 'abuses' the avatar state to cheat, she's only doing it for a short period of time and thus isn't shown to be exhausted. However, if she where to stay in the Avatar state for an extended fight, she would eventually become drained and be more vulnerable than if she had not tapped into the avatar state at all.

3. Korra is the first Avatar of a new Cycle:

   In book 2 Korra was separated from Raava, and was forced to fight without the Avatar spirit. Just before harmonic convergence ended Korra was able to rejoin with Raava, but in doing so she started a new Avatar cycle and could no longer tap into the knowledge and wisdom of the past Avatars. Due to this Korra is less confident in the avatar state; she is willing to tap into it in trivial times, but in more desperate situations she's less likely to allow herself to become vulnerable.

4. When she is chained; she is actively resisting going into the avatar state:

   Zaheer knows that the only way to kill the Avatar and end the cycle is to kill Korra while in the avatar state. Korra is poisoned and trapped, but keeps fighting to stay out of the avatar state; knowing that she is vulnerable in the avatar state (point 1), and knowing her time is shorter if she taps into that power (point 2), she also isn't confident enough in her current state to break out even in the avatar state (point 3). She sees that her only course of action is to fight it for as long as possible in the hopes of being rescued or dying outside of the avatar state. She eventually loses control and switches into the avatar state; but is surprised when she is able to bend her way out of her bonds and is able fight back.