Anyway, as you may have guessed, there are several different Acts of Contrition. In fact, as long as you believe it, you can say a simple I'm very sorry God, and you're good. I hope I am not sounding flippant, because that is the last thing I want to do.
Anyway, here a few examples of some Acts of Contrition.
Act of Contrition (Authorized for usage in Ireland)
O my God!
I am heartily sorry for having offended Thee;
and I detest my sins above every other evil,
because they displease Thee,
Who for Thine infinite goodness art so deserving of all my love;
and I firmly resolve,
by Thy holy grace,
never more to offend Thee,
and to amend my life.
Act of Contrition (Authorized for usage in England)
O my God,
I am sorry and beg pardon for all my sins,
and detest them above all things,
because they deserve Thy dreadful punishments,
because they have crucified my loving Saviour Jesus Christ,
and most of all because they offend Thine infinite goodness;
and I firmly resolve,
by the help of Thy grace,
never to offend Thee again,
and carefully to avoid the occasions of sin.
Act of Contrition before Holy Communion #1
I desire, O my Saviour,
I grieve from my inmost heart that I have ever offended Thee by my sins, T
hee my God and my chief good,
Thee who art so gracious to me,
and so oft refreshest me in Thy Blessed Sacrament.
I grieve especially for the sins of [name(s) of the person(s)]which Thou knowest, Thou searcher of our hearts,
and which I, a miserable sinner,
do confess in the bitterness of my soul.
Would that I had never offended Thee!
Yet a contrite and humble heart,
O God, Thou wilt not despise;
Thou who for love of us didst give to us Thine Only-Begotten Son,
to wash us from our sins in His own Blood.
For you fans of Latin
ex toto corde poenitet me omnium meorum peccatorum,
eaque detestor, quia peccando,
non solum poenas a Te iuste statutas promeritus sum,
sed praesertim quia offendi Te,
summum bonum, ac dignum qui super omnia diligaris.
Ideo firmiter propono,
adiuvante gratia Tua,
de cetero me non peccaturum peccandique occasiones proximas fugiturum. Amen.
O MY God,
I am heartily sorry for having offended Thee
and I detest all my sins because of Thy just punishments,
but most of all because they offend Thee,
my God, who art all good and deserving of all my love.
I firmly resolve, with the help of Thy grace,
to sin no more and avoid the near occasions of sin.
Have a glorious day!