Is there a single word for "The excitement and enthusiasm at the beginning of a new job/romance" etc.?

In my native language, there is a single word to express the high energy and enthusiasm shown by many at the beginning of a new job/project/romance etc. Normally it is used with a bit of skepticism/sarcasm.

I am looking for a single word or phrase in English that expresses the same

Solution 1:

Honeymoon period is often used to refer to this time.

any new relationship characterized by an initial period of harmony and goodwill.

Solution 2:

Novelty is related, particularly on the "used with a bit of scepticism" point. It typically indicates, if not enthusiasm, some level of interest found in a new and different situation.

"My new job is amazing!"

"Let's see if you still think that when the novelty's worn off."

Solution 3:

Limerance: The magic of chemistry that happens in our brains when we fall in love.

Limerence has also been defined in terms of the potentially inspirational effects and the relationship to attachment theory, which is not exclusively sexual, as being "an involuntary potentially inspiring state of adoration and attachment to a limerent object involving intrusive and obsessive thoughts, feelings and behaviors from euphoria to despair, contingent on perceived emotional reciprocation”. -Wikepedia

Solution 4:

Honeymoon period and infatuation are the two terms that spring to my mind.

Solution 5:

The initial rush, though often used of drug induced euphoria or an adrenaline surge, can also be used to indicate the high of a new job or romance:

There's no way to fully recreate that new job feeling, but leaders can promote the ingredient that fuels the rush of a new job...
The rush of making a new friend can most definitely be likened to the rush of a new romance, things just feel a tad more exciting