The discovery that the narrator makes by dissecting his brain is learning that his thoughts require a constant flow of pressurized air because brain activity slows due to low air pressure.
He’s bleeding I believe is the answer.
Answer:

<em><u>nice</u></em><em><u>❤</u></em>
<em><u>Never</u></em><em><u> </u></em><em><u>regret</u></em><em><u> </u></em><em><u>what</u></em><em><u> </u></em><em><u>makes</u></em><em><u> </u></em><em><u>you</u></em><em><u> </u></em><em><u>happy</u></em><em><u>¡</u></em><em><u>!</u></em><em><u>!</u></em><em><u> </u></em>