I'm translating a book named "the Psychology of Selling", in which there is a sentence:

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But even though I hurried from prospect to prospect, and spoke louder and faster to each person, I was barely holding on by my fingernails.
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Here, what does "barely holding on by my fingernails" mean? Does it mean to keep the prospect or to stay in the trade for a living?

Looking forward to your help.

Calli.

I have never heard the idiom, supposing it is one, but the writer is describing an on-going struggle to keep one step ahead of failure. Imagine someone hanging from a cliff; they do not have a firm handgrip, but are hanging by their fingernails, and could fall at any moment.

A more familiar expression to me is:

Quote:

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by the skin of one's teeth by a very narrow margin; barely : I only got away by the skin of my teeth. [ORIGIN: from a misquotation of Job 19:20: “I am escaped with the skin of my teeth” (i.e., and nothing else). Current use reflects a different sense.]

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EDIT: Or, given the context:

I was just scraping by
I was just getting by
I was barely managing
I was circling the drain e.t.c.

So, to answer your question, the writer means that he or she was able "to stay in the trade", but only just.