Be anxious for nothing, but in everything by prayer and supplication, with thanksgiving, let your requests be made known to God; and the peace of God, which surpasses all understanding, will guard your hearts and minds through Christ Jesus.
(Philippians 4:6-7)

Worry or anxiousness is a lack of trust that the Lord Jesus Christ will not take care of your needs.  When you trust and yield your will to the Lord Jesus Christ you give Him free reign to be involved in your life.

Let them shout for joy and be glad, Who favor my righteous cause; And let them say continually, “Let the LORD be magnified, Who has pleasure in the prosperity of His servant.”
(Psalm 35:27)

When there is worry or anxiousness in your life, your will does not allow the Lord Jesus Christ to intervene on your behalf.  Praying in the Spirit will train your spirit to yield and submit to God’s will and plan for your life.  Praying in the Spirit will also increase your faith and trust in God dramatically!  “But you, beloved, building yourselves up on your most holy faith, praying in the Holy Spirit” (Jude 1:20).

The more time you spend with God the more you will yield your will and trust and rely on Him.  When you worry you are totally consumed in the very situation and then your eyes will be off of the Lord.  “Casting the whole of your care [all your anxieties, all your worries, all your concerns, once and for all] on Him, for He cares for you affectionately and cares about you watchfully” (1 Peter 5:7 Amplified).  When your eyes and heart are fixed on The Lord continually that allows Him to move mightily and freely on your behalf.

“And which of you by worrying can add one cubit to his stature?  “If you then are not able to do the least, why are you anxious for the rest?  “Consider the lilies, how they grow: they neither toil nor spin; and yet I say to you, even Solomon in all his glory was not arrayed like one of these.  “If then God so clothes the grass, which today is in the field and tomorrow is thrown into the oven, how much more will He clothe you, O you of little faith?  “And do not seek what you should eat or what you should drink, nor have an anxious mind.  “For all these things the nations of the world seek after, and your Father knows that you need these things.  “But seek the kingdom of God, and all these things shall be added to you.  “Do not fear, little flock, for it is your Father’s good pleasure to give you the kingdom.”
(Luke 12:25-32)