Do not fret or have any anxiety about anything, but in every circumstance and in everything, by prayer and petition (definite requests), with thanksgiving, continue to make your wants known to God. Philippians 4:6 (AMPC)
Anxiety is always the result of allowing our minds and hearts to carry and so be weighed down with cares and troubles we are not able to do anything about.
Do not be anxious therefore is “do not allow your mind and heart to carry and so be weighed down with cares and troubles you’re not able to deal with.
Now of course the cares and troubles do exist and they will come to our minds and hearts. But thank God He’s given us a solution. Instead of carrying the cares and troubles, cast them to the Lord. He alone is able to carry them. When cares and troubles come, cast them to the Lord in prayer and thanksgiving. Talk to Him about everything that bothers you and thank Him for taking care of it. That will take off your head and chest the whole weight of it.