HELP ME PLSS NOW OMG PLSSSSS IF YOU SEE THIS HELP ME

As Ma and Ba think about whether or not they
should let Minli try to change their fortune, Ba says it is like trying to find the paper of happiness.

In the story he tells, the secret of happiness is shared, but it is lost. What do you think was written on the missing paper?

What one word might be the secret to happiness? Why do you think this?