The phrase is casual and more common in informal situations or personal conversations.

Informal Context

Shows strong emotional response; indicates that the annoyance is not trivial.

Emotional Intensity

Often used for emphasis, not to be taken literally.

Suggests the annoyance is distracting or preventing concentration.

Indicates the degree to which one's feelings are negatively affected.

The phrase can be an exaggeration, not meaning the annoyance is the worst thing ever.