Sforno on Deuteronomy 14:1/ספורנו על דברים י״ד:א׳

1בנים אתם לה' אלוקיכם, לא תתגודדו, it is bad manners to display excessive grief over the loss of a relative as long as a more relevant relative (G’d) is still alive. This is why G’d reminds us in this context that we are His children, i.e. that whatever relative we may mourn we have a father who is alive and well so that we are not really orphaned.

2ולא תשימו קרחה בין עיניכם על מת כי עם קדוש אתה, there is no reason to mourn excessively for the person who has passed as he, at least, has not experienced any loss, on the contrary, he has been promoted to the region of eternal life, something of which our sages in Avot 4,6-7 have said that a single hour of the serenity experienced in that life is worth all the combined delights ever experienced during one’s transient life on earth.