Positive vibe
Generate excitement
When user receives a negative message (deny access, error messages, etc), deliver the message in a tailored way that will minimize the negativity as much as possible, by carefully consider the appropriate language, colors, illustrations that can be used in the message.
This principle should be applied thoroughly in the app's language, images, illustrations, etc.

Positive reinforcement
Consider creating micro-actions to encourage users to continue with the flow or provide visual feedback during an interaction. This includes but not limited to the use of language, images, illustrations, animation, sound, icons, colors, etc.