Note there are two very similar Chinese characters here. 曰 and 日. The first is wide and the second is narrow and long. They are two different characters. The first 曰 is seldom used today and means "say" as explained earlier. The second one means "day".
Here is the first ten digits in Chinese, starting from one. 一二三四五六七八九十.
吾 is the old character for "me".
曾子 was another student of Confucius. 曾 was his family name, his given name was 參. He was 46 years younger than Confucius - one of Confucius young student. Here 曾參 reflected on how he learnt.
I reflect upon myself three times every day.
The three questions 曾參 asked himself everyday are:
When I work for other, did I do my job faithfully?
Here the key word is 忠 which is made up of 中 and 心. 中 means "middle" and 心 means "heart". When combined, 忠 means the faithful attribute towards doing a job so that one would not regret - peace to the mind.
Am I not trustworthy to my friends?
信 is made up of 人 and 言. 言 means "words". The words from an honorable man is "trust"-worthy.
Do I practice what I have learnt?
習 appeared right at the beginning of Analects - "子曰：學而時習之，不亦說乎?". 習 means "practice". The character 朋 in 朋友 also appeared at the beginning - "有朋自遠方來，不亦樂乎?" These were the words of Confucius explaining the attitude towards learning. Here 曾參 explained the 'how' of putting 學問 into everyday practice. As noted before, to Confucius, learning is not about knowledge or career path, it is more about building a good personal character.
When we are doing a job, we put all our effort in with all our heart. When interacting with friends, we keep our promise. We reflect on all these good character daily and aim to practice them. That's Confucius concept of a gentleman. His moral system starts with self. The next entry will be extending this concept into society.