“Succeed in” or “succeed at”

Interesting question.

When I tried to search for an answer to your question, I had many more hits for succeed at than succeed in, and no easy source wherein a grammatical comparison is made. Succeed in was often followed by a context (school, life), whereas succeed at was often followed by what might be considered a task (being yourself, work, divorce, psychometric testing.)

From this, I would guess both are common, and it might be up to your discretion which you use.

I do think they carry different connotations. (Please forgive the redundancy.) To succeed in life means something very different to me that to succeed at life. To me, to succeed in implies to do well within a context (life), whereas to succeed at implies doing well in conquering a task (life).

To succeed in life, one must succeed at being oneself. (my nonsense, not the words of anyone else.)

I hope this helps.