Sentence:  I kept account of every farthing I spent, and my expenses were carefully calculated. Every little item such as omnibus fares or postage or a couple of coppers spent on newspapers, would be entered, and the balance struck every evening before going to bed. That habit has stayed with me ever since, and I know that as a result, though I have had to handle public funds amounting to lakhs, I have succeeded in exercising strict economy in their disbursement, and instead of outstanding debts have had invariably a surplus balance in respect of all the movements I have led. Let every youth take a leaf out of my book and make it a point to account for everything that comes into and goes out of his pocket, and like me he is sure to be a <WSD>gainer</WSD> in the end. 
Meaning of the word marked with <WSD> tags:  One who gains a profit or advantage.