'Seriously' in the Bible

For he will not often consider the [troubled] days of his life, because God keeps him occupied and focused on the joy of his heart [and the tranquility of God indwells him].

But there was found in it a poor wise man, and by his wisdom he rescued the city. Yet no man [seriously] remembered that poor man.

Yes, if a man should live many years, let him rejoice in them all; yet let him remember the days of darkness, for they will be many. All that is to come will be futility.