Let us not become weary in doing good.
I think the context of this verse suggests rather more than physical tiredness. What Paul is warning against, quite simply, is getting fed up with doing good! Dont give up, he goes on to write, but, as we have opportunity, let us do good to all people. (v 10). This reminds me of the One who always went about doing good. There is no reference in the Gospels to him being too tired, cold, hungry, busy, preoccupied or just plain weary to do good. As in all things, our lovely, selfless Saviour provides the supreme example for us to follow.
Daily Reading: Ezekiel 33