If its been a string of blanks try: All the fish have been ottered!
If looking for an excuse to cover just the one day's blank:
Starting with Tarker (again). Otter, crayfish, Pike, zander and/or cormorant in your peg.
Water to low and clear, (flipside) water to high and coloured.
You forgot to pack the bait that
would have worked.
You had to pack up just as they were going to feed.
Somebody had already fished the best swims earlier in the day.
To much weed, making it impossible to present a bait properly.
Dog walkers skylining you and/or dog swimming in the water.
Herd of cattle in the field that wouldn't leave you alone, of course this one has many alternative culprit animals; sheep, horses, goats.... etc
Joker fishing above or to the side of you kept over-casting your swim.
As you can tell, I've plenty of experience in this field of the sport.
Of course there is the, I'm having an off day, if it was easy there'd be no rewards in the capture
OR I'm cr@p and fish for ego boosting comments.