I have a Capricorn 12th house and Aquarius 1st house.
Most of the times I have irritation (and usually I am a calm person) is when the Moon is transiting my first house, and also on those months when Mars or the Sun transits the first house (havign Aquarius rising, this occurs in February).
Since 2000, I have had irritation nearly every time Mars transited my first house (Jan 2000, Dec 2001, Aug 2003, May 2005, Apr 2007, Apr 2009 and Feb 2011.
Several irritation days have also occurred as the Sun transited my first house in Feb 2004, Feb 2006, Feb 2008, Feb 2009 and Feb 2011. This is about half of the February months!
Often, it has also resulted in clashes and conflicts, even break-ups, and in a few lucky ocasions, in impulsiveness to take decisive steps forward in my life.
Then, it is interesting to state that my only big depression on my life, when I was 18, was as Uranus entered my first house (but Saturn was also entering the fourth house at that time).
Finally, the Moon transits. I had often seen that depression tended to come when the Moon transited Aquarius and Pisces, at my first house. This year, I noted I have irritation and even depression in several ocasions when the Moon transited the first house (2 Feb, 27 Feb, obviously the February month, but there were also many other irritation days on that month, 20 May, a major irritation on 21 Jun which resulted on a big step forward in my job, 14 Jul a depression, 1 Dec depression, 24 Dec, 28 Dec).
Curiously I noted that these difficult Moon days tend to occur as the Sun transited angles, as in February (after crossing the ASC), May (in fourth house), July (just before crossing the DSC) and December (after crossing MC). Besides the first house, they also tend to occur when the Moon transits other water houses or the sixth house, on those months.
Now that I got the pattern, I ask why? Sometimes it is good because it triggers me to take decisise steps, but often this extra energy is trouble. What do I do with it? How? Why does it happen? There is no point in being able to predict when it is going to happen, if I cannot learn how to best deal with it!
I guess this is a question of duality, of life itself and why the Universe was created. In fact, God, the Creator not only created the Universe to manifest and experience itself, but it also created duality, a big illusion, so that every soul can experience one thing as opposed to another (good versus bad, warm versus cold...).
Do we have free will? Certainly there is a fate when the Moon transits angles it triggers a burst of energy, where we feel impulsive, depressed, irritated, more prone to take decisise steps forward. So, the energy is there. There is no hidding, there is nothing else we can do to bury it; I should not avoid being energetic when the Moon transits my 1st house, that's just the way it is. The key is deciding how to use that extra energy in the best light - that is my free-will. Or at least it seems. I believe than when we transcend duality, we transcend this problem of knowing how to behave in those days; there is no struggle, no duality.
But i assume the purpose of the Universe, the Creator, is to have experiencing one thing as opposed to another: creative and individualistic and impulsive energy (first house) as opposed to the interconnected peaceful but potentially lazy and melancholy energy of the twelfth house. And so on, at every angle.