Mental awareness of negative thoughts can help us with our own wellbeing (How mental awareness interferes with negative thinking - Elemental.medium.com)

It can be the weather and just going shopping. 

If the day is blustery and rainy, with water puddles everywhere and cars spraying everyone with water as they speed by, it can make our day go badly if we feel cross all day. 

Mindfulness in moderation can help us to feel that calming our mind and looking at what's angering us can contribute to our wellbeing.

Elementa.medium.com explains how mental awareness can interfere with negative thinking:

Why Mental Self-Awareness Is Good for Your Brain