The most common cause is depression.
I hope this hellps you.
Answer: Appreciation
Explanation: For managing time effectively and therefore completing the edition of the challenging issue, which translates to meeting up with deadline, Jessy took her team out to lunch as a show of appreciation for the work done. In simpler terms, Jessy is grateful or thankful for her team of editors work and effort.
I’d like to say all above, but like if not all than everything besides reading a book