Angels are normally invisible to us (1 Cor 11:10, LOP note). They can appear to us in human form (Dan 9:21) so we can listen and talk to them (Eccl 5:5, JB). Furthermore, they differ in strength (Dan 10:13, CEV), have emotions (Ps 103:20, EVD), can get tired (Dan 9:21, GW), and are viewed as soldiers (Ps 103:20, EVD) who have a hierarchy (Heb 12:22, ASB note). Each is given their own responsibility (Heb 1:14, Barclay) over some aspect of creation (Rev 16:5, NAB; Rev 7:1, IVPBBC note). Indeed, many thought that an angel was assigned to everything (Gal 4:3, WSNT note).
In fact, there was a widespread Jewish belief that each person has a guardian angel. Most commentators also see this as a New Testament view (Mt 18:10 cf. Osborne, Matthew, p 680). Acts 12:15 may further add the popular idea that this angel was the person’s spirit-counterpart who could look like the person (see commentators on this verse like Bruce, Barrett, Kistemaker, Fitzmyer etc.). It was believed this angel might appear independently during the person’s life (Acts 12:15, TNT note) or after the person’s death – where a person who sees it might think they are seeing the dead person’s ghost (Polhill, Acts, p 282).
Why should any of this matter to us? Since angels watch us (1 Cor 11:10, Weymouth note; Ps 138:1, LXX), we should behave in ways that show them respect (1 Cor 11:10, JB) because they tell God about our activities (Eccl 5:5, JB note). That they go to God for safety (Ps 36:7, EVD) and depend on the aid of the Holy Spirit (Rev 17:3, CEV) should remind us of our even greater need to do this. They are to serve God’s children (Heb 1:14) by protecting us (Gen 32:1, CW) as guardians (Mt 18:10) and encouraging us in various ways (Lk 22:43, Knox). Even churches seem to have an angel or angels assigned to them (Rev 2:1, TEV). We should thank God that He cares so much for us as to assign us angelic help.
Instead of being timid, learn to be appropriately bold.