Halachically Complete
The Chazon Ish introduced a concept that he felt was necessary for perfecting one’s character. He calls this דקדוק הדין, or meticulousness in the performance of Mitzvot.
He explained that when one is trying to improve his character, the acceptance of the truth of Halacha is mandatory. One must realize that he is not capable of being more compassionate and just, than the law that originated from Hashem at Sinai.
The meticulousness in observing Halacha demonstrates a consistency in how one observes Judaism. Just as he is aware and shows alacrity in how he treats others, he must demonstrate this same alacrity in the manner in which he observes the law.
He should not do things in a haphazard manner, where he does only what is necessary. On the contrary, when he is careful to follow each law to its detail, he shows a reverence for the law just as he shows reverence for Hashem, Himself.
This means that he doesn’t just build a Succah, but he makes sure it is Halachically correct. The same might be true of the Tefillin or Mezuza that he purchases. Are these items fit according to Halacha?
When one demonstrates that the details of the Halacha matter, it is also an indication that he cares about studying the Torah as well. This concept of דקדוק הדין is not something to be taken lightly. The Chazon Ish believed that this is a necessary ingredient towards making one’s worshipping of the Torah more complete.