Purity of Intention - To do all things for love of God and His glory and to unite our will with His will
Vainglory attempts to steal glory from God for yourself. It sneaks in later on to ruin good things, like eating to excess after originally eating for necessity

"Beware of practicing your piety before others in order to be seen by them; for then you have no reward from your Father in heaven. So whenever you give alms, do not sound a trumpet before you, as the hypocrites do in the synagogues and in the streets, so that they may be praised by others. Truly I tell you, they have received their reward. But when you give alms, do not let your left hand know what your right hand is doing, so that your alms may be done in secret; and your Father who sees in secret will reward you. And whenever you pray, do not be like the hypocrites; for they love to stand and pray in the synagogues and at the street corners, so that they may be seen by others. Truly I tell you, they have received their reward. But whenever you pray, go into your room and shut the door and pray to your Father who is in secret; and your Father who sees in secret will reward you." - Matthew 6:1-6

But he said to them, “I have food to eat that you do not know about.” So the disciples said to one another, “Surely no one has brought him something to eat?” Jesus said to them, “My food is to do the will of him who sent me and to complete his work." - John 4:32-34

"Render service with enthusiasm, as to the Lord and not to men and women" - Ephesians 6:7

Remedies for Vainglory

1. St. Bernard says to recognize it before it gets you, saying vainglory only kills those who are inconsiderate and negligent.

2. "Never say any thing of yourself that may redound to your praise, though the person you speak to should be one of your most familiar friends; but on the contrary endeavour to hide all your virtues, with more care than you take to hide your vices and imperfections." - St. Bernard (Bern. in formulâ honestæ vitæ)

3. Hide your good actions so that only God knows about it.

4. If you are not able to hide your good actions, purify your intention and offer all your thoughts, words, and actions.

5. Know yourself. It will lead to humility to fight vainglory.

How do we know when we have a pure intention?

1. Not envious when others do well: But if you have bitter envy and selfish ambition in your hearts, do not be boastful and false to the truth. Such wisdom does not come down from above, but is earthly, unspiritual, devilish. For where there is envy and selfish ambition, there will also be disorder and wickedness of every kind. But the wisdom from above is first pure, then peaceable, gentle, willing to yield, full of mercy and good fruits, without a trace of partiality or hypocrisy." - James 3:14-17

2. A holy indifference to whatever we are assigned in our state of life, as long as follow God's will.