For Love or From Love

When you look at some people it is hard to tell if what motivates them is for love or from love. Let me explain.
Under the old covenant people obeyed because they wanted God's love upon their lives. Their favourite verse of Scripture was, "We love Him so that He will love us."
Under the new covenant people obey because they are loved by God. Their favourite verse is, "We love Him because He first loved us.:
I was reading in Psalm 18 this morning. It struck me the contrast between two paragraphs. The first tells us of the Gospel, we do because we are loved.
16 He reached down from on high and took hold of me;
he drew me out of deep waters.

17 He rescued me from my powerful enemy,
from my foes, who were too strong for me.

18 They confronted me in the day of my disaster,
but the LORD was my support.

19 He brought me out into a spacious place;
he rescued me because he delighted in me.

The next paragraph seems to be in contrast.

20 The LORD has dealt with me according to my righteousness;
according to the cleanness of my hands he has rewarded me.

21 For I have kept the ways of the LORD;
I have not done evil by turning from my God.

22 All his laws are before me;
I have not turned away from his decrees.

23 I have been blameless before him
and have kept myself from sin.

24 The LORD has rewarded me according to my righteousness,
according to the cleanness of my hands in his sight.

Why do we serve God? Is it for love or from love?
When I hear some preachers say that God will bless us financially, or health wise or other we know that they are serving God "for love" rather than "from love." If you were to tell them that they were following the old covenant they would deny it but that is not the Gospel. The health and wealth gospel is another gospel it is not the Gospel of grace.