Thanks for the info on Francis de Sales, Narkissos. I've had similar wrestlings with the predestination question, a hangover from my RC days - I didn't get myself into as bad a state as he did thankfully! Now my ideas on heaven, hell and salvation have changed so I don't think I have so much issue any more.
I found the work 'On Loving God' by Bernard of Clairvaux very helpful - this is possibly the work which set me on the path of exploring why I worship/love God.
'You want me to tell you why God is to be loved and how much. I answer, the reason for loving God is God Himself; and the measure of love due to Him is immeasurable love.'
'On a lower plane of action, it is the reluctant, not the eager, whom we urge by promises of reward. Who would think of paying a man to do what he was yearning to do already? For instance no one would hire a hungry man to eat, or a thirsty man to drink, or a mother to nurse her own child. Who would think of bribing a farmer to dress his own vineyard, or to dig about his orchard, or to rebuild his house? So, all the more, one who loves God truly asks no other recompense than God Himself; for if he should demand anything else it would be the prize that he loved and not God.'
The later chapters describe four degrees of loving God - for selfish reasons, loving out of thankfulness, loving God - just because He is God and finally complete denial of self to dwell in God's love (Bernard said only the martyrs were likely to get this far before death).