Frustration isn't the same as anger, but it's a near cousin. It's a reaction to an obstruction of some sort to what you want to do. Anger is more a reaction to having been wronged. Both are pretty normal human emotions.
In either case, there's definitely a choice about what to do next. The recommendation to pray for the person whose behavior led to anger in the post above is a good one. You can also try stepping back from frustrating situations (particularly ones that aren't immediately resolvable or which you do not have the power/authority to resolve the underlying situation) and think about how it could be an opportunity.
Here's an example from my life. I work for a Catholic hospital which recently moved from the old building (about 50-60 years old) to a new building. When they designed the location, they did not allocate adequate parking spaces. Administration knew it was a problem and just did nothing.
Well, my department was one of the early ones to move (I am not in patient care) and I knew it was going to be a disaster because with less than a third of the employees (and no patients), the employee parking was full and overflowing. Patient move day was on a Sunday, so on Monday ... it was BAD. People who were going to the medical plaza (dr's offices) drove around for an hour and left in frustration because they couldn't find parking, employees had to park in patient spots, down the road ways and it was just horrific. I would arrive 45 minutes before I had to so that I could be there when third shift was departing (and then stalk a departing 3rd shift worker for the parking spot). I'm quite frankly surprised that it didn't come to blows anywhere for a parking spot. Suddenly, this problem impacted administration and they hired tractors to start putting in more parking, renting a parking lot and running a shuttle bus for employees, and so forth. Stuff that they should have figured out before we ever moved, but they just "oh, it'd cost too much to put in a garage" or otherwise stick their heads in the sand like the workers could just magically beam in ala Star Trek.
Well, I had also recently experienced a shift in job duties and a shift in job hours. The shift was only a half hour later, but it really isn't something I'm happy about (my middle son has an after school activity which generally gets out around the time that I used to get off work so that it worked well for me to head over to get him ... now he has to wait up to a half hour or walk home two miles carrying the weight of the world [ok, I exaggerate slightly, but he's a high school student plus the equipment for his sport] on his back. And with the parking, basically I felt like I had to give work a free half hour of my time. I was resentful. I was frustrated! I was even on the border of angry.
Well, I talked to my brother-in-law, and this situation was one of the ones that we discussed. He said, "You have such a wonderful opportunity!" And he then pointed out that it takes about twenty minutes to pray the Rosary, so after I found my spot, I could just find myself a quiet place and pray a Rosary.
So, I started to do that. There's a chapel in the hospital (and being a Catholic hospital means that in the chapel there's a Tabernacle). It has changed my demeanor to the point that coworkers have noticed. I still don't like the change in my hours. But now that one of the lots is in, and the parking is actually easing up a little, I still get there 35 minutes early so I have plenty of time to park and walk into the chapel, pray, and then make my way to my work station.
And as far as anger--yes, it can be entirely justified to be angry at an injustice/untruth/wrong done to yourself or someone you care about. The question is ... what do you do with that anger? As I have told my youngest son, anger and hatred are poisons that can eat your soul. Praying for the person or situation that led to anger is the best medicine.