1 Kings 3:3–Solomon showed his love for the Lord by walking according to the statutes of his father David, except that he offered sacrifices and burned incense on the high places. 
It can seem almost simultaneous to strive after the Lord, while still struggling with a mentality from a past we’ve been redeemed from. That we find ourselves like the apostle Paul, “...when I want to do right, evil lies close at hand” (Romans 7:21).  That we can be godly about this, while “devilish about that…
Sacrificing at “high places” were permitted by God, because there had yet to be a permanent place for people to go and offer their sacrifices.  But these sacrifices became misguided and a major place for idolatry, even for King Solomon! (1 Kings 3:2, 1 Kings 11:7)
In coming out of “the world”, things were emphasized that may not be evil, but have a place in our hearts, that could compete with our worship of God and become a  “high place”.  Solomon loved the Lord, but he had a “high place” that he made time for, which was originally for the Lord, but became a place of idolatry.  Anything or anyone can become a “high place”.  A mentality can be a high place, that we cherish and hold onto, though we love the Lord…
The goal like King Hezekiah is to fight to tear down all “high places”, which comes by an obedient faith to Jesus, and our minds being renewed by the Word of God (2 Kings 18:4, 2 Corinthians 10:4-6).  So if we don’t take “high places” seriously, they readily replace the Lord in our affections and become a place of worship for us, compromising what God gave us to manage for His glory…
1 Kings 11:6-8-So Solomon did what was evil in the sight of the Lord and did not wholly follow the Lord, as David his father had done. 7 Then Solomon built a high place for Chemosh the abomination of Moab, and for Molech the abomination of the Ammonites, on the mountain east of Jerusalem. 8 And so he did for all his foreign wives, who made offerings and sacrificed to their gods.