Marina, hello. Our Faith is peace and joy in the Holy Spirit, where there can be no fear, but perfect love from the Father which casts out all fear. Why is there no fear!? Because there is no law that judges/condemns and imputes to us (the children of God) sin. There is no law, therefore there are no rules, memorized samples on how to pray and when, because where there is the Spirit of the Lord, there is Freedom. How your Spirit prompts you inside to pray, pray in this way without any doubt or fear, for the Lord sees the heart, and He does not await verbosity, how it is normal for hypocritical people.
If, for example, you will be coming to your earthly father daily and say the same memorized words, won’t he think that there is something wrong with you!? Because otherwise you might as well record your words of prayer and play them back when needed!?
God is the Living God and He accepts the Living worship and prayer, from the heart, when you as a child simply open before Him your inner-self. Also, prayer isn’t only when you call to God, but it is also when God speaks to you in your conscience, for you to hear Him, be edified, be comforted and joyous in having fellowship with Him, and this kind of fellowship does not seize, it is like the breath of faith. Just like David wrote in Psalm 15:7, that his interior preaches even in the night.
And a bit about groanings. If, for example, in your life you have a difficult situation, which you cannot resolve, and you even have no words to express what you are experiencing, then in this case only groanings remain in your heart which God also hears and certainly sends you an answer and consolation.