What is significance?

If I were a janitor, I would feel insignificant. Do all/most/many janitors feel that way?

On the other hand, I also feel insignficant doing face recognition research that doesn't seem to advance the state of the art but merely reproduce what others have published.

Is significance reliant on the size or merit of the contribution to society?

If I "do everything as unto the Lord", does that make my work significant regardless?

If I were out there saving lives physically and/or spiritually every day, would it be possible to be insignificant? Or is that type of work significant regardless?