Then an angel from heaven appeared to him and gave him strength.

He created the angels and now deigns to accept their consolation, though not in need of it.  Perhaps the angel couldn't resist.  Perhaps it is the unique nature of this angel that he dares to offer his creator consolation.  Maybe he burst from heaven upon the special permission of the Father.

If Jesus accepts such tokens of love as this from the angels, perhaps he will accept them from us too.  "Remain here and stay awake with me." (Matthew 26.38)