I try not to forget what it felt like to be a new employee
what it felt like to be new(相手と仕事の話をしている)/what it felt like to be a new employee (仕事の話かどうかより曖昧な場合)
新入社員の時の気持ち
the feeling of being a new employeeもOKですね。個人的にwhat it felt like~で始まる表現の方が自然に感じますね。
例えば、
It's been 10 years since I joined this company, and there are more people who are reporting to me, but
入社して10年がたち、部下も増えてきたけど、
I try not to forget what it felt like to be a new employee
新入社員の時に持っていた謙虚な気持ちを忘れないようにする
ご参考になれば幸いです。