I zipped myself all the way into the sleeping bag of myself, not because I was hurt, and not because I had broken something, but because they were cracking up.
This lines hows despondent tone
Explanation:
Despondent is in depression from loss of hope or spirit feeling or showing profound despair, dejection, discouragement, or gloom:It is tone showing fully depressed hopeless or in gloom or having no courage.
<em>I zipped myself all the way into the sleeping bag of myself, not because I was hurt, and not because I had broken something, but because they were cracking up. </em>This is the line that reveals a despondent tone.<em> </em>