The sinners happiness is not what God is seeking to achieve in HIS disciple. What God does achieve in the converted sinner is salvation and the knowledge of salvation. The sinner can obey only because of grace and the indwelling Holy Spirit. Hence the saved sinner knows joy by the grace of God and knows his/her sin by the same. One brings joy the other brings fear and doubt. Both are in Christian experience.
Galatians 5:17 For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
Romans 7:18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. 19 For the good that I would I do not: but the evil which I would not, that I do. 20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me. 21 I find then a law, that, when I would do good, evil is present with me.
From article "“I just want to encourage everyone of us to realize when we obey God, we’re not doing it for God – I mean, that’s one way to look at it – we’re doing it for ourselves, because God takes pleasure when we’re happy."
This could be a natural development of the Arminian ideology, we observe so often on the board.