This is usually considered a Royal Psalm.   In the Book of Common Prayer of the Church of England, Psalm 101 is prescribed for use at the anniversary of the monarch’s ascension- Allen, 8; Goldingay, 139

The Psalm describes the kind of person the king longs to be and who he hopes to surround himself with. The people we surround ourselves with influence us for good or evil and the people the king surrounds himself with influence the whole nation.
David's high aspirations were not realized in his personal life. His personal failures had a negative impact on the whole nation (II Sam. 11-12; I Kings 1:5-6).

Jesus and Psalm 101
“No clear echo of Ps. 101 occurs there, but ultimately the Christians will view the psalm in light of Isa. 11:1-5. It becomes a testimony to the One, who did all things well (cf. Heb. 4:15 ; 5:7), who, endued with the spirit of wisdom, has been appointed Judge of the world (Acts 17:31 ) and whose servants are called to be above reproach (cf. Titus 2:14 )” Allen, 7.

101:1 The mercy of the LORD opens the door of salvation- Eph. 2:4.

101:2 Blameless is a key word in the Psalm and the same Greek word is used in vs. 2 and 6. Christ is without blemish- Heb. 9:14 ; I Peter 1:19 - and is a word used to describe the people- Eph. 1:4; 5:27 ; Col. 1:22 ; Phil. 2:15 ; Rev. 14:5.
It is because He is the blameless sacrifice that we can be blameless before Him. 

101:8 kill in the LXX is used for what was done to Jesus in Matt. 16:21 ; 17:23 ; 21:38-39; 26:4

101:8 Sinners is used for those for whom Jesus died- Rom. 5:8- and came to save- Matt. 9:10-11, 13; 11:19 ; I Tim. 1:19
It is because of HIs death that we can be forgiven. 

This is all so that we would have access to God’s city- Rev. 21-22