Jesus goes hard in the paint in Matthew 6. He gets past all the surface level crap and gets right to the heart. He's not trying to play games with his audience. He's not trying to play games with you and I, either. He talks about good things we, as Christians, should all strive to do: give to the needy, pray, fast, and not worrying. Those are all great things, right?
They CAN be right things. If your heart is in the right place. Jesus ends this chapter by saying, "Seek first his kingdom and his righteousness" He doesn't end it by saying "Do first his kingdom and his righteousness"
Prayer is great. If you're not praying, you're not growing. Fasting is great. Giving up food to get more traction with God is always refreshing. Trusting God is great. God will provide for us, so we have no need to worry.
But if you're praying to be seen, it's not great. It actually won't get you anywhere with God. If you're fasting so that people can see how "dedicated" you are to God, it's not great. It'll make people think you're more religious, but won't get you anywhere with God. If you're worrying and running after what the world can give you as security, you'll be doing what every other person in the world is doing that DOESN'T follow Jesus.
Here's the key to all of the subjects Jesus talks about in Matthew 6: Seek first.
When you're praying, seek first God more than seeking the answer to a prayer. When you're fasting, seek first God more than secretly wanting to lose those love handles. When you're trusting, seek first God more than you're trusting your bank account to bail you out. When we seek first the Lord, "all these things will be given to you as well."
Seek first His kingdom and His righteousness, and the rest will work out, because our God provides for those that seek Him above all else.