Can 把握 mean "self control"? I'm trying to figure out what ”把握“ actually means （it seems to have a number of meanings that don't align with any translation in english). One sentence, that I thought was interesting was "她的把握全失去了" (referring to an instance where a girl is beginning to have an affair with a guy. What does it mean in this sentence? Does it mean self-control? 

Another sentence that was used at the end was “可是她现在不同了，她现在是个自主、有把握的女人。 
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把握 means seize; grasp; hold. It's rarely used in its literal sense but the metaphorical sense is just that.

把握住今天。Seize today.
他对成功很有把握。Success is within his seize.

To have 把握 in something you need both confidence and ability, although when people say 有把握/没有把握/失去把握 they are actually emphasizing on the confidence side, e.g.

我有把握拿满分。I have confidence in getting full marks in the exam.

失去把握 can also mean lose control, though not necessary 'lose control over oneself'.
In your first sentence, &quot;她的把握全失去了&quot;, there are two possible interpretations.

She lost her 'seize' (confidence or leverage) in the affair.
She lost her 'seize' (control) over herself.

From the limited context in your question I am unable to tell which one is it. In addition to the plot, it also has a lot to do with the author's language style.
Similarly, the second sentence has two possible meanings &quot;她现在是个自主、有把握的女人。&quot;

She has become a woman of determination and confidence (she has general confidence in her own actions and decisions).
She has become a woman of determination and means (she has a lot of levers/maneuvers in the things she does).

That again depends on more context to nail down.