Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God. And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus.
Not to be anxious is a command and to disobey a command is sin. We are to always trust God and never be anxious about the things of life. It does not mean that we become irresponsible. But that we do what we are capable of doind at that moment and leave the rest to God to work things out in His own time.