Been there, done that for 20 years. Same words said every mass.
If the words are repeated, does that make them somehow invalid? Are the prayers that Jesus and the Apostles prayed every week at synagogue “vain repetitions” because they prayed them the same, week after week? I realize they were vain for you, because you were not walking with God, and you did not recognize Him present.
kujo313;2214992:
We should not worship any creature, not even the blessed Mary. We must worship God only. We can never love Jesus too much; He is our Creator who takes care of us and all the universe. He became man for our salvation and died on the cross to save His people from their sins. I love the Lord Jesus too. He is the very purpose of my life and my sincere desire is to honour His name.

This is very Catholic of you, kujo!
Yet we understand that Mary is not the saviour herself.
Yes, we do understand that. We also understand that Jesus has made her a partaker in His ministry of salvation and reconciliation. She is our model, and exemplifies what Jesus wants to do in the lives of each of us. If we say “Let it be done to me according to Thy Word,” this will happen.
Every Christian should consider Mary with respect. She is forever to be called blessed.

Great kujo! Very Catholic of you.
Yet, I think it is a sign of disrespect when people expect from her things that she cannot give.
I suppose this is true. If Mary were not “in Christ” she would be able to offer us little of value. It is her eternal resting place with Him that releases His grace through her. God wants to release this same grace in all of us, which is why we are enjoined to pray for one another.
Why would people pray to her,
Because the effectual fervent prayers of a righteous person avail much.
when the Bible clearly teaches us that we should pray to God and that God alone knows our hearts (1 Kings 8:39)?
This is a common protestant misunderstanding. Since Mary is in the communion of saints, and the saints are all in the presence of God, when we pray, we join our prayers with them. There is no division or separation from God.
Why would people ask grace from Mary, when the Bible teaches us that all grace comes from God (1 Peter 5:10)?
This is a good question. All grace does come from God. Scripture tells us that Mary is “full of grace”. There is no room left in her that lacks in grace. This is a very special state. Where grace abounds, sin cannot exist. Why ask grace from her? She is a vessel through which it flows. We see that God has ordained that His grace should flow through people.
Acts 5:15
15 Insomuch that they brought forth the sick into the streets, and laid them on beds and couches, that at the least the shadow of Peter passing by might overshadow some of them."
Do you think it was Peter whose shadow healed the sick? No, it was the grace of God, working in this manner. Doesn’t it make sense to run and get under the shadow if you need healing? Does that mean they were worshipping Peter, or his shadow? Surely not!
Acts 28:8-9
Paul visited him and prayed, and putting his hands on him healed him. 9 And when this had taken place, the rest of the people on the island who had diseases also came and were cured."
The text here says that Paul cured the people with diseases. Yet, we know that it was not Paul himself, but Christ within him through which the grace flowed. It is true, some did misunderstand this and thought Paul was a god of some kind, but he was quick to correct them.
8 And Stephen, full of grace and power, did great wonders and signs among the people."
This passage says that Stephen did great signs and wonders. But we know this was all done by the HS through him, not by Stephen himself! Acts 6:8-9
12 Now many signs and wonders were done among the people by the hands of the apostles." Acts 5:12
Is it right to worship the Apostles because grace flowed through them? No. But we honor them for their obedience to God, and for being good vessels through which His grace is poured, and examples for us.