In the following sentence as an example :
"he sweated it out until the lab report was back", 
What does "it" refer to in "sweated it out"?

I have just seen the example "if it wasn't for Amber.." which looks like "Without Amber ..". How could we change "I swaeted it out" so to make it more obvious like Amber's example?

English is a foreign language for me and I have no problem understanding Amber's example. The example"I lost it" could be understood as I lost control or composer. In the same way how could I understand the sentence in my question which sounds very alien to me as a french and Arabic speaker. I'm interested in the etymology or grammar of it, or in which way could it be transformed.