Some Christians, when first coming across St. Paul’s teaching, see this text in a negative way: interpreting it as a call to a form of humility, that requires them to think of themselves in a ‘downward’ manner; bordering on self- deprecation.   But St. Paul does not actually say that.
Instead, he says: ‘Do not think of yourself more highly than you ought’: indicating that Christians should think of themselves ‘upwardly’; and as highly as is proper to their calling – which, in Christ, is high indeed.
Our gospel text (Matthew 6:19-34) confirms this, in several positive ways: as it points out the contrast between the things of earth, and the things of heaven. It not only encourages us to make the right choice; but also makes it clear that ‘heaven’ is not a place that may, or may not await us, at some time in the future: but is the realm of God’s presence; to which, through divine grace; the believer already has access in the here-and-now of the present.
Christ gave many teachings in this matter; some of which use complex images, explainable only in theological terms: but in our text at Matthew 6; he uses simple, poetic images than soon persuade our hearts and minds to know that: ‘He is talking about us!’  Happy in that knowledge: we can turn back to St. Paul’s teachings, and discover much further encouragement in what he has to say about Christians.
Paul’s entitlement to speak confidently about life-changing, life-enhancing things of the Spirit; is illustrated in his Damascus Road experience, where Christ says, of him: ‘This man is my chosen instrument to carry my name before the Gentiles and their kings…’ (Acts 9: 15).
It is in that further knowledge that we hear his words afresh: ‘Do not think of yourselves more highly than you ought, but rather think of yourself with sober judgement, in accordance with the measure of faith God has given you’.
What is ‘the measure of faith God has given you’ actually like? At Luke, chapter six, amid various teachings about what God expects of us; and what we may expect of God; Jesus says this:- ‘Give, and it will be given to you. A good measure, pressed down, shaken together and running over, will be poured into your lap. For with the measure you use, it will be measured to you’ (V.38).
Christ’s image points to our Heavenly Father as being like a good miller. In ancient Israel, men, rather than women, went to buy flour. They would sit on a low stool, with the measure on their laps. A ‘bad’ miller, simply filled the measure to the brim: and the purchaser, as he walked homeward, would find that the flour had so shaken down, that there was little more than a two-thirds measure, by the time that he got home. In positive contrast: the ‘good’ miller would fill the measure to the brim; and then with sundry shakings, pressings and further fillings, come to the point where the flour was so tight-packed, that it began to flow over the edges of the measure, into the purchaser’s lap.
That, said Jesus, is the sort of measure that Christians may confidently expect to receive from their Heavenly Father.
St. Paul, who is Christ’s agent, and our teacher: encourages us to put that understanding to work in our own lives. 
He says that ‘sober judgement’, applied through our God-given ‘measure of faith’, enables us recognize just where we are at; how we came to be there, and what blessings will be brought into being through our faith.
At Galatians 4:5, Paul says that, in Christ, we have become spiritually adopted. Adoption is always a deliberate act; and so it was, and remains, with God; as he ‘adopts’ all who turn to him through Christ: accepting them as they are, with a strong hope of what they will become.
At a time when there were far more babies available, than there were adoptive parents: a married couple decided to adopt three children. Having chosen, and received into their family, two perfectly formed babies: they made a particular decision in relation to the third child; and chose a mentally disabled baby who, without adoption, had no hope of normal family life.
Love like that is wonderful: but, far greater, is the foundation of love upon which the ‘Family of God’ is built.
Because: ‘All have sinned, and fall short of the glory of God’ (Rom 3:23) the Lord does not seek perfection in us. Instead, he adopts us as we are; spiritually disabled: and, through mercy, love and grace, works towards our betterment.
What he does seek; is our deliberate, life-changing acceptance of Christ, as our personal God, Saviour and Lord. Then, with the Holy Spirit to guard and direct us: we are led into the perfection that our ongoing acceptance of Jesus gradually brings about.
St. Paul; who is Christ’s agent, and our teacher; also says that, at its very best, and most lovingly functional; the Christian Church reflects the qualities, attributes and fullness of Christ (Eph. 1:23).
Being a realist, Paul teaches that none of this ‘just happens’; but is made to happen; through the Church building itself up, in love and grace, and being, as Christ to the world all around it.
Paul said: ‘Do not think of yourselves more highly than you ought, but rather think of yourself with sober judgement, in accordance with the measure of faith God has given you’.
Before St. Paul came on the scene: the whole concept of ‘think upwardly about yourself’ was given particular credence and validity by Christ: in a direct teaching to his followers, and within a prayer about his followers.
At John 14: 6, Jesus says: ‘I am the way, and the truth, and the life’.  He also says: ‘I am the light of the world; he who follows me will not walk in darkness, but have the light of life’ (John 8: 12). Now consider this.  Jesus also says: ‘You are the light of the world. Let your light shine before men, that they may see your good deeds, and praise your Father in heaven’
‘I am the light’ and ‘You are the light’? However, there is no contradiction at all. What Jesus is saying; is that the ‘life’ that is his, and the ‘light’ that is his, are given in trust to his followers, to live out, and to show forth.
Finally, this ‘living out’ and ‘showing forth’ is given a particular emphasis by
Jesus, in what is known as his ‘Great High-Priestly Prayer’, to the Father.
Taking up almost the whole of chapter 17, in John’s gospel record: the prayer forms a summing-up of Christ’s earthly ministries.
It includes six particular touches on glory: five of which refer to the glory that belongs within the relationship of Christ, with his Heavenly Father. But, the sixth one is very different.
At verses 9+10, we find Jesus holding up his followers, in prayer, and asking that they should be kept spiritually safe.
At one point, he says: ‘I pray for them. I am not praying for the world, but for those you have given me, for they are yours…’All I have is yours, and all you have is mine. And glory has come to me through them’.
St. Paul says: ‘Do not think of yourself more highly than you ought’: indicating that Christians should think of themselves ‘upwardly’; and as highly as is proper to their calling – which, in Christ, is high indeed.
This wonderfully positive thinking, is not original to Paul: for Christ himself says that we should live, think, speak and act as him, in this needy world; in such a way that…
…what we are, speaks clearly of who we are; Christians; whose lives give ongoing testimony to the glory of God, as revealed in Jesus Christ.   Amen.