If you're using 'succeed' in its usual sense - meaning 'be successful'/ manage to do something - the ONLY correct construction is 'succeed' + in + Ving'. For example: He succeeded in climbing the mountain. They succeeded in solving the mystery. She succeeded in persuading him to apply for the job. Succeed + to would be wrong in any sentence such as those above. If you come across anyone saying 'He succeeded to win', for example, this is a non-native error. I'm sure that the internet is full of such examples, but never forget that the internet is full of terrible English. The only context in which 'succeed to' is possible is when you are talking about royalty and statespeople assuming a certain position. For example, 'The prince succeeded to the throne'. This is formal, relatively rare and (of course) a different meaning from the sentences above. General rule - forget about 'succeed to'.

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.