Once, the Philistines, people who were enemies of our God's people, during a war, they stole the Ark and took it to their city. Because of this, many bad things happened with them. And the same thing happens when people keep their Tithes and Offerings instead of giving them to God, both Tithes and Offerings are sacred and we cannot keep what belongs to Him friends.
In the Bible passage where God says to His people to bring Tithes and Offerings to His house, He also promises to rebuke the devourer spirit because he destroys things. That's why those who don't keep their Tithes and Offerings are blessed, because God rebukes all bad things from their lives.
It's the Holy Spirit that gives us direction of how we should give our offerings. The blessings of God come to our lives through obedience, and for us to obey God, we need to make a lot of effort right friends? And this effort is a sacrifice! You have to make a big effort to wake up early, go to school, listen to your friends picking on you, not to lie, not to disobey, to be a different child, when you do this, you are sacrificing and this is also an offering that you are giving to God. But you need to do this with much joy! Don't forget that, for you to receive the Holy Spirit, you have to make efforts and give the best of your heart to God.
"So let each one give as he purposes in his heart, not grudgingly or of necessity; for God loves a cheerful giver." 2 Corinthians 9:7 (NKJV)