'The servants of the Lord are deeply afflicted by seeing ungodliness and violence prevail; especially among those who profess the truth. No man scrupled doing wrong to his neighbour. We should long to remove to the world where holiness and love reign for ever, and no violence shall be before us. God has good reasons for his long-suffering towards bad men, and the rebukes of good men. The day will come when the cry of sin will be heard against those that do wrong, and the cry of prayer for those that suffer wrong. They were to notice what was going forward among the heathen by the Chaldeans, and to consider themselves a nation to be scourged by them. But most men presume on continued prosperity, or that calamities will not come in their days. They are a bitter and hasty nation, fierce, cruel, and bearing down all before them. They shall overcome all that oppose them. But it is a great offence, and the common offence of proud people, to take glory to themselves. The closing words give a glimpse of comfort.'

Matthew Henry Concise Commentary, Habakkuk 1:1-11

Theology, however important it may be to study, becomes an idol if it becomes knowing more about God rather than knowing Him more.

Go therefore and make disciples of all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, to the end of the age.

Matthew 28:18-19

There are many professing Christians who know of God's love, but yet there are few who truly know God's love. Test yourself therefore: do you truly know God's love, or is it purely a matter of half-hearted head-knowledge?

'The Christian world is in such a deep sleep; nothing but a loud shout can awaken them out of it.' -- George Whitefield

Just for clarification: Legalism is the teaching that works create, or, at least, contribute to one's salvation. Sanctification is the teaching that salvation creates, or, at least, contributes to one's works via the Holy Spirit.