phrasal-verb
look back upon
過去に起こったことを考える、しばしば複雑な感情を伴って
Meaning
to think about something that happened in the past, often with mixed feelings
Example
When I **look back upon** my decisions, I wish I had chosen differently.
自分の決断を振り返ると、違う選択をしていたらよかったと思います。