Matthew 6:29 is part of what is known as The Sermon on the Mount. Jesus is teaching us within chapter 6:1-18 not to seek recognition from others by making a public display of our giving, prayers and fasting. In doing these things for public recognition, Jesus is telling us that the receipt of such recognition by men is our full reward and is not recognized as righteousness by God. Our Lord knows the heart and it's true motives. He knows that those types of prayers, giving and fasting are not done for Him in love and worship, but rather are done for selfish reasons.
Jesus teaches us how to pray in what is often referred to as the "Lords Prayer". Within Jesus' example of prayer the focus is on God. Our Father, Hallowed be Thy name, Thy kingdom, Thy will. Jesus also identifies our basic needs, our daily bread, forgive us our sins, lead us not into temptation, deliver us from evil. Then Jesus finishes His example by repeating that our focus is to be on God, For Thine (His) is the kingdom, power and glory.
Continuing in verses 19-34 we find our verse about the lilies of the field as Jesus teaches us about the futility of seeking after wealth and the things of this world through anxious concern. Jesus said in verses 28-29 "And why are you anxious about clothing? Observe how the lilies of the field grow; they do not toil nor do they spin, yet I say to you that even Solomon in all his glory did not clothe himself like one of these." He is teaching us that, in spite of all our ability and efforts, mankind cannot even match the splendor of one of His flowers. Therefore, put not your needs and concerns within this world before your worship of God when even the beauty of something like a flower is beyond your control. Jesus says in verse 8 that God knows what our needs are before we even ask.
The theme of chapter six is that it is Gods kingdom and glory that we are to seek, with a true heart, and He will provide for our needs, which are forgiveness of our sins and deliverance from evil through Christ, Jesus. Our Father will also provide us with what we need to sustain ourselves. When our focus is on Him we will be anxious for nothing. Verse 33 says "But seek first His kingdom and His righteousness; and all these things will be added to you." Trust God with your needs. For by all his own efforts, ...even Solomon in all his glory did not clothe himself as one of these." Observe the lilies of the field.
To God be the glory