Sentence:  Gratiano: / ...I owe you much, and, like a wilful youth / That which I owe is lost; but if you please / To shoot another arrow that self way / Which you did shoot the first, I do not doubt, / As I will watch the aim, or to find both, / Or bring your latter hazard back again, / And <WSD>thankfully</WSD> rest debtor for the first. 
Meaning of the word marked with <WSD> tags:  In a thankful manner; giving thanks.