We're a good two years late with today's yo-ji, as it would be most appropriate had we published it during the year of the boar. But since we're not going to wait another ten years for it to cycle back around (Hell, Nirav might not even LIVE another ten years), looks like boar's on the menu today!
猪(いのしし; inoshishi) is the kanji for 'wild boar,' which can still be seen in mountainous parts of Japan. On the Okayama leg of my hitch-hiking trip, I was in a car that almost ran one over, and my driver was actually disappointed that we hadn't. Why? Because inoshishi meat is delicious.
突 is most commonly found in the verb 突く, meaning to 'pierce' or to 'prick,' as in 「針を突く」; it has a general connotation of 'stabbiness,' but here it might be better read as "thrust."
猛 gets attached to just about anything to make it 'fierce,' 'violent,' 'wild,' or 'intense.'
And 進, you'll recognize from 進む, to move forward. It means 'progress,' which you may recall from 日進月歩.
1. Pig-headedly powering forward.
2. Foolhardiness; recklessness
3. Diving in headlong without considering the consequences.
As you may have noticed, this yo-ji makes an excellent companion to yesterday's 表現 Break: 生兵法は大怪我のもと. While 生兵法は大怪我のもと describes the results, 猪突猛進 applies to the person who acts on nothing but 生兵法 and ends up with the 大怪我.
Beyond characterizing people who happen to be 猪同士, like yours truly, this phrase is useful in lots of ways. It can be broken down into it's component parts, for example. 猪突: all the recklessness with none of the progress, or 猛進: a mad dash without necessarily connoting high levels of risk (think "a mad dash to the finish line).
And it doesn't always have to be a bad quality. Just as in English, people who are stubborn sometimes get praised for their stubbornness. Someone who sets their mind on achieving a goal and get it done no matter what it takes, that could fall into the realm of 猪突猛進. After all, charging forward without heeding the consequences can have positive results, right?
And when advising someone not to worry so much and just go for it, to just dive in and see how it goes, you could use the same phrase, as the 四字熟語 データバンク does in their example sentence, which we will borrow:
What if you stopped worrying about failure and just went for it? You might be surprised by how well it works out.
Final note: for some reason, this example sentence really, really makes me want to link 疑心暗鬼, so here it is. Maybe you could tell someone was 疑心暗鬼になっている to 失敗を恐れず猪突猛進してみて？