Addiction

• "Just wan son. Honest! Wee half at the end of the day. Just helps me tae unwind."

  Davie stifles his emotions with alcohol. He seems to be deliberately underplaying the amount he is drinking
• "Maybe ma coupon'll come up this week."

  Davie resorts to alcohol to stifle his feelings, and gambling to resolve his financial woes
• "Just a wee half when ah finish ma work."

  Again, Davie underplays the drinking he's doing. It appears as a crutch - a means of support as he struggles to cope.
• "Best part ae a week's wages."

  Davie has lost a large amount of money to the bookie. His desperation to escape poverty has made him reckless 
• "It's a mug's game. The punter canny win."

  Billy is more realistic than Davie, and he's frank with him. Gambling will benefit the bookie, not Davie.
• "There was gonna be nothing left after ah'd paid the light bill. Had tae take a

  chance."

  Davie, instead of paying the bill, has gambled the money. He is desperate for better things, and this fuels his reckless behaviour.
• "Ah suppose it's the feelin you've at least got a chance."

  This is a fairly heartfelt admission - Davie feels so helpless that he clings to the illusion of hope