Hexagram 1, Qián (The Creative): Line 3
乾卦九三 · 乾为天 · 中文版
九三：君子终日乾乾，夕惕若，厉无咎。
The line (Legge)
In the third NINE, undivided, (we see its subject as) the superior man active and vigilant all the day, and in the evening still careful and apprehensive. (The position is) dangerous, but there will be no mistake.
Small Image commentary
'Active and vigilant all the day:' - (this refers to) the treading of the (proper) path over and over again.
象曰：终日乾乾，反复道也。
In plain words
The noble person is active and vigilant all day, and still watchful and self-examining at night; the position is dangerous, but there is no fault. The third line is at the top of the lower trigram, just below the upper one, neither here nor there, which is why it is dangerous; diligence and self-examination are what keep it free of fault. The Small Image says that, going back and forth, it keeps to the right way.
Applying it to your situation
If you hold a position between those above and those below, under real pressure, this line suggests working fully by day and reviewing by night, which helps more than worrying. What from today is worth looking at again? Take care, too, that diligence does not turn into exhaustion that never stops.
Position
A solid (yang) line in the third place, which is a yang (odd) place, so it is in its proper place. Its partner is line 6; both are yang, so they do not respond.
If this line moves
With this line moving alone, Qián changes into Hexagram 10 Lǚ (Treading). The Jiaoshi Yilin verse for this change (Chinese): 焦氏易林·乾之履.
A recorded case from Takashima
Qian to Lü: Matsukata Masayoshi asks about the harvest: After a spring of deep snow, long rains and unusual cold, the finance minister Matsukata Masayoshi feared a poor harvest and asked Takashima to divine it. The third line of Qian, "active all day long", was read as a year of drought in which the crops would still ripen.
The hexagram
Hexagram 1 Qián (The Creative). The Judgment: Qian (represents) what is great and originating, penetrating, advantageous, correct and firm.
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English text: James Legge, The Yi King (Sacred Books of the East, vol. 16, 1882), public domain, as transcribed by the Chinese Text Project. Chinese: the received text. Offered for study and reflection, not as prediction. Plain-English readings and position notes by this site.