Over many years of being a Christian I've heard a ton of sermons and Bible studies tell me that we should not worry. I'm getting up there in years, so I'm gonna guess I've heard, oh, 112 of these talks. They say we're commanded not to worry and tell us to stop. Sometimes they suggest that we think about something else--don't focus on your worries, focus on your blessings. End of lesson.
I doubt that anyone who has preached such a sermon has seriously wrestled with anxiety. In fact, I don't think I've ever heard a sermon on worry from someone who has seriously dealt with it or lived with it. Like every major spiritual challenge we face, it is nearly impossible to "just stop" but as I read chapter 6 I wonder if it is because we get the focus wrong just a bit. Jesus is saying that we don't need to worry, but His main point is the goodness of God. He says God is generous and good and wants to provide good things for us. Jesus' focus is not on getting us to behave correctly, but on God.
I hear the sermons, and I know that I'm commanded not to worry, so when I worry I don't just worry, I also feel bad about worrying. All those sermons and talks take a tough situation and make it worse by layering guilt on top of anxiety. I have this impulse to pull up my socks, and beat myself up until I stop worrying. I don't think this is what Jesus intends, if for no other reason than "feel bad until you feel good" seems like bad advice. I think Jesus intends to give us permission to rest in the goodness of God. Wright says Jesus was basically a happy guy, and that feels right to me.
One other note--Jesus says in v 25 "isn't the body a greater thing than clothing?" I don't like to disagree with Jesus, but my clothing is definitely better looking than my body.