What is a synonym for eustress?

There isn't a perfect synonym for "eustress" as it's a specific term for positive stress. However, here are some phrases that convey similar meanings:

General Positive Terms:

* Beneficial stress

* Healthy stress

* Positive stress

* Constructive stress

* Productive stress

* Motivating stress

* Growth-promoting stress

More Specific Phrases:

* Challenge stress

* Excitement

* Motivation

* Enthusiasm

* Engagement

* Flow state (This refers to a state of complete absorption and focus)

The best choice will depend on the context and the specific nuance you want to convey.