Therefore, when we couldn't stand it any longer, we thought it good to be left behind at Athens alone,
The significance of Paul's being left alone derives from the fact of his enemies seeking to kill him, the threat being so serious that an escort guarded his journey to Athens.  The poignant mention of "alone" in this verse suggests that Paul recognized the danger of his unguarded exposure; and as his name was already known throughout Athens following his address on Mars Hill, he must have been very apprehensive of what could easily befall him.  Thus his consent to be left alone derived from a genuine love of converts and the utmost unselfishness on his own part.