You can renew the baptismal vows which your parents would have offered for you when you were an infant, and incapable of making them yourself -- and so spiritually renew and reenter into the graces of your baptism -- which has always been with you and helped you, since you were an infant.
Be full of gratitude for your baptism!
Baptism is what make one a Christian, what allows you to go to Confession, and partake of all the Holy Sacraments. I think of desire to be baptised again as an adult as perhaps truly a desire to fully realize the graces given in the past -- to make a good confession and act of contrition, perhaps feeling the weight of sin, venial or worse mortal, and so spiritually fulfill the more the baptism one has already received and partake of sanctifying grace.
You cannot be baptized again, but you can draw on the graces, perhaps long neglected anew.
'Every Christian has renounced the world and its pomps at baptism. This vow does not oblige you to live like a hermit, but it certainly obliges you to something. It is not an empty promise.'
St. Claude de la Colombiere
'Before holy baptism, grace encourages the soul towards good from the outside, while Satan lurks in its depths, trying to block all the intellect's ways of approach to the divine. But from the moment that we are reborn through baptism, the demon is outside, grace is within.
Thus, whereas before baptism error ruled the soul, after baptism truth rules it.
Nevertheless, even after baptism Satan still acts on the soul, often, indeed, to a greater degree than before. This is not because he is present in the soul together with grace; on the contrary, it is because he uses the body's humors to befog the intellect with the delight of mindless pleasures. God allows him to do this, so that a man, after passing through a trial of storm and fire, may come in the end to the full enjoyment of divine blessings. For it is written: "We went through fire and water, and Thou hast brought us out into a place where the soul is refreshed" (Ps. 66.12).'
St. Diadochos of Photiki
'What were you before Baptism but the unhappy slave of Satan, and subject like him to eternal punishment? But by Baptism you have been delivered from this unhappy subjection, through the divine alliance which you have contracted with Jesus Christ, which procures you the enjoyment of eternal happiness, if you observe all its conditions.'
St. Jean Eudes
'Repentance is the renewal of baptism. Repentance is a contract with God for a second life. A penitent is a buyer of humility. Repentance is constant distrust of bodily comfort. Repentance is self-condemning reflection, and carefree self-care. Repentance is the daughter of hope and the renunciation of despair. A penitent is an undisgraced convict. Repentance is reconciliation with the Lord by the practice of good deeds contrary to the sins. Repentance is purification of conscience. Repentance is the voluntary endurance of all afflictions. A penitent is the inflicter of his own punishments. Repentance is a mighty persecution of the stomach, and a striking of the soul into vigorous awareness.'
St. John Climacus
'We who have received baptism offer good works, not by way of repayment, but to preserve the purity given to us.'
St. Mark the Ascetic
'Baptism is the sacrament of Christ's death and Passion, according as a man is born anew in Christ in virtue of His Passion; but the Eucharist is the sacrament of Christ's Passion according as a man is made perfect in union with Christ Who suffered.
Hence, as Baptism is called the sacrament of Faith, which is the foundation of the spiritual life, so the Eucharist is termed the sacrament of Charity, which is "the bond of perfection" (Colossians 3:14).'
St. Thomas Aquinas