I think the trick is coming to the understanding that none of this is really mine, so I don't really have anything to hold on to. It becomes easier to give when it isn't mine--I'm just holding it for God. I have to ask myself, "What would God do with this?" regardless of what the "this" is--and especially if the "this" is money.
I can take what God gives me and just use it for myself, but then I'm like the servant in the parable who buries the talent--the landlord gave the talent to be used, to be invested and spent as the landlord would do.
The disciples come to Jesus and tell him to send the crowd away because they need food. Jesus says "What do you have?" and the little that can barely feed the twelve of them and Jesus is used to feed five thousand men, their wives, and their children--and they end up with more leftovers than the little they started with.
What do you have? Is it so necessary to you that you are unwilling to part with it, or use it for another? Will you bury it in the ground to keep it safe? Or will you take that little bit you have, regardless of how crucial it is to you, and share it, give it away, and trust God to take it, multiply it, satisfy the other and give you back more than you gave?
But it's not really yours anyway. It belongs to God. And this is never more true than if you claim to be God's--if you belong to God than all that you are, all that you have, belongs to God. What would God do with it?
God gives it to me to use. It isn't that God doesn't want me to have nice things, but God certainly doesn't want me to justify my extravagance either. God wants me to have, but he wants others to have too--God gives to me because he expects me to give to them. It's not really mine anyway, the second I convince myself that it is mine, I become a thief and a robber--a murderer by default who will let many die from lack, just so I can have an extravagantly nice car and live in a luxurious home.
So if you take what God gives you and only use it for yourself because you feel you deserve it, or earned it, or because you think it is yours, then by all means enjoy it. Enjoy all the things that money can buy you, because it is the only reward you will ever get. Live well for a season; but there will be weeping for an eternity.
For all of this belongs to God, even eternity. If I cannot be trusted with a little, then I cannot be trusted with a lot. If I cannot be trusted with God's things for this short season, then I cannot be trusted with them for eternity.
So, I think the trick is coming to the understanding that none of this is really mine, that it becomes easier to give when I understand that what I'm giving isn't really mine, but I'm holding it in trust--I'm just holding it for God. So I ask myself, "What would God do with this?"