A thorough study of this question would be very helpful. Some of our correspondence schools in Europe have issued lessons on the topic.

Chap. 306 - We shall Meet Our Guardian Angels

He shall give his angels charge over thee, to keep thee in all thy ways. Psalm 91:11. {Mar 314.1}

Not until the providences of God are seen in the light of eternity shall we understand what we owe to the care and interposition of His angels. Celestial beings have taken an active part in the affairs of men. They have appeared in garments that shone as the lightning; they have come as men, in the garb of wayfarers. They have accepted the hospitalities of human homes; they acted as guides to benighted travelers. They have thwarted the spoiler's purpose and turned aside the stroke of the destroyer. {Mar 314.2}

Though the rulers of this world know it not, yet often in their councils angels have been spokesmen. Human eyes have looked upon them. Human ears have listened to their appeals. In the council hall and the court of justice, heavenly messengers have pleaded the cause of the persecuted and oppressed. They have defeated purposes and arrested evils that would have brought wrong and suffering to God's children. To the students in the heavenly school, all this will be unfolded. {Mar 314.3}

Every redeemed one will understand the ministry of angels in his own life. The angel who was his guardian from his earliest moment; the angel who watched his steps, and covered his head in the day of peril; the angel who was with him in the valley of the shadow of death, who marked his resting place, who was the first to greet him in the resurrection morning--what will it be to hold converse with him, and to learn the history of divine interposition in the individual life, of heavenly co-operation in every work for humanity! {Mar 314.4}

With the word of God in his hands, every human being, wherever his lot in life may be cast, may have such companionship as he shall choose. In its pages he may hold converse with the noblest and best of the human race, and may listen to the voice of the Eternal as He speaks with men. As he studies and meditates upon the themes into which "the angels desire to look" (1 Peter 1:12), he may have their companionship. {Mar 314.5}

Here is what EGW wrote about guardian angels:

Though the rulers of this world know it not, yet often in their councils angels have been spokesmen. Human eyes have looked upon them. Human ears have listened to their appeals. In the council hall and the court of justice, heavenly messengers have pleaded the cause of the persecuted and oppressed. They have defeated purposes and arrested evils that would have brought wrong and suffering to God's children. To the students in the heavenly school, all this will be unfolded. {Mar 314.3}