The meal-offering which the High Priest is commanded to offer twice each day is described as having the volume of "a tenth of an ephah [approximately 2.3 litres]. . . half in the morning and half in the evening" (Leviticus 6:13). The Torah does not say "a twentieth of an ephah in the morning and a similar amount in the evening" stressing that the two halves form one complete whole.
Rav S R Hirsch (on 16:5) suggests that this impresses upon the bringer of the offering, and on us, that "the rules of the universe and the relations of human beings to them, were the same in all the various and contrasting conditions of life, as typified in the contrasts of day and night". The offering that the Priest brings in the morning, when he is fresh and ready to face the day, is half of the same offering of the evening, when he reflects on a day well-spent or not.
All of the time, and in all of our moods, we are obliged to serve Hashem with the same enthusiasm, because each moment of service is a part of one continuous whole.