Mathew 18:10 See that you do not despise one of these little ones. For I tell you that in heaven their angels always see the face of my Father who is in heaven. (ESV)
Jesus speaks here in response to the disciples question "Who is the greatest in the kingdom of heaven?" (v. 1). This whole secton seems to be about how we treat other people: Don't cause others to sin (v. 6); Forgive your brother (v. 15-35). And here, God diligently seeks out the one lost little sheep (v. 12-14).
If someone is irritating you, you may need to do a heart check. That "little one" is precious in the eyes of God. They may be acting out because of some past hurt. Try to understand. Encourage and call to account: "admonish the idle, encourage the fainthearted, help the weak, be patient with them all" (1 Thes. 5:14). You might be better to have a great millstone fastened about your neck and be thrown into the sea (v. 6) than to offend one of these little ones.
Oh God, grant me to be patient with them all. That I might be humble like a child. I have been forgiven much. Grant me a big, generous heart toward others.
In Jesus' name - Amen,