I think I did a good job even though it was super hard working there.
ご質問ありがとうございます。
前職がシフト勤務でめちゃくちゃ大変で、「自分でも[よくやってた](https://eikaiwa.dmm.com/uknow/questions/76000/)なって思う」と伝えたいなら、英語で「I think I did a good job even though it was super hard working there.」と言えます。
ご参考になれば幸いです。
自分でもよくやってたなって思う
- I even thought that I did a good job.
- I don't know how I did it. (どうやったんだろう。)
- I even think that I did good.
前職がシフト勤務でめちゃくちゃ大変で、それを振り返ってみて自分でもよくやってたなって思う
- My last job was crazy hard shift work, and I look back on it and wonder how I did it.
- My last job's shift work was incredibly challenging and looking back on it I even think that I did a good job. I have no idea how I did it.
アメリカ合衆国 
