I've had similar problems as what you described- the headaches, moodiness/irritability, and focus issues.

The gels with caffeine offered some relief, as rij73 mentioned.

I have also found relief by checking my breathing and doing some slow deep breaths to help myself relax. Also, doing some on the bike stretches and moving things around (stretching neck by moving head side to side and up and down, rotating my shoulders, etc). And, I noticed that when I start to get these feelings, I get even more tense (even to the point of gritting my teeth), so I do have to play some mental games to get myself in a better frame of mind.

So, for me, it's been a combo of the caffeine and relaxation techniques that have helped.