Do not lose heart, it is just a _ in the teacup.

Explanation

The phrase 'storm in a teacup' is an idiom used to describe a situation where there is a lot of fuss or excitement about something that is not important. 'Storm' is the correct word that completes this idiomatic expression. The other options, 'wind,' 'cyclone,' and 'blast,' do not fit because they either imply a different scale of disturbance or lack the idiomatic context.