We are asked to be vigilant in the strengthening of our testimonies and our relationships with Christ, and we know that vigilance is required to overcome the daily battle with the adversary.
We might have the intention to do this every day, but it is possible to put in our best effort consistently?
Can there be no days where fatigue gets the best of us?

While this is a fair question, I think it is just that - a question asked out of exhaustion.
We know the answer.

Perhaps then, what we should ask for is the strength to carry on, in the moments when we feel inclined to offer less than our best.