"'It is not by strength that one prevails; those who oppose the Lord will be broken. The Most High will thunder from heaven; the Lord will judge the ends of the earth. He will give strength to his king and exalt the horn of his anointed.'" NIV translation
Hannah ends her worship looking forward to the Messiah. She sang about the fact that it is the power of the Christ that overcomes the world. Just as her body did not have the strength on its own to produce the son, we too do not have the power to overcome this world on our own.
"Then Elkanah went home to Ramah, but the boy ministered before the Lord under Eli the priest." NIV translation
Samuel was left under the direction of the priest and Hannah returned home. He would have performed routine duties such as cleaning and carrying things.
We do not know what went through his head but it would have to be hard having your mother and father leave you behind.
"Eli's sons were scoundrels; they had no regard for the Lord." NIV translation
While Samuel was a servant of God, Eli's sons were not. The Hebrew word that is translated as "scoundrel" is "beliyyaal" and it really means worthless, ungodly, and wicked. They had no concern or respect for the things of God and so they truly were worthless. That may not be popular to say in our world today but, without God, there is nothing that we can do or say that will have any lasting effect. This may sound harsh but the simple fact of the matter is that our lives are to be continual worship of the Lord. If that is not happening, then, we truly have no purpose (are wicked and worthless). This is basically what the entire book of Ecclesiastes is about and the wisest man ever (Solomon) came to that conclusion. It is also important to note that it was not the environment that the sons had grown up in as they had evidently grown up in a godly home. Their problem was not external (their surroundings) but internal (their hearts).