To understand anxiety, you need to examine the Psychology of the Mind and the Science of Wellbeing.
The Mind has a tendency to overestimate the emotional effect of both good & bad events. Misleading intuitions can quickly become a focus of negativity.
But our Minds can adapt and naturally find a path through crisis. This is especially so, if reinforced by using coping techniques to strengthen our Psychological Immune System, which integrates our cognitive, motivational and behavioural personality traits that provide a defence against stress.
This is why, if we routinely practice Mindfulness type techniques, we establish good mental resilience and create strong positive neuropathways within the Mind.