If I set out to buy things for myself that I like, the quality and quantity of what I am able to buy is going to be limited, because of the limits of my funds. But if instead I buy to give, then God shall give to me - and God is far better resourced than me to be able to afford the quality and quantity that I desire and need. Therefore what I end-up obtaining will be far better, and in the meantime my focus can continue to be God and others. If I put Him first and give to others, He will give me what I need and desire. And I'd rather it be Him than me that's in charge of my needs and desires. Meanwhile I get to be an agent of His provision for others; and above all - I remain free to focus on Him Who is the source of all true enjoyment in life.
That's better than a win-win situation - it's a win-win-win situation. Praise the Lord!