This is great stuff from Calvin on the necessity of prayer. Really warm and instructive.
...Therefore, even though, while we grow dull and stupid toward our miseries, he watches and keeps guard on our behalf, and sometimes even helps us unasked, still it is very important for us to call upon him:
First, that our hearts may be fired with a zealous and burning desire ever to seek, love and serve him, while we become accustomed in every need to flee to him as to a sacred anchor.
Secondly, that there may enter our hearts no desire and no wish at all of which we should be ashamed to make him a witness, while we learn to set all our wishes before his eyes, and even to pour out our whole hearts.
Thirdly, that we be prepared to receive his benefits with true gratitude of heart and thanksgiving, benefits that our prayer reminds us come from his hand [cf. Ps. 145.15-16]
Fourthly, moreover, that, having obtained what we were seeking, and being convinced that he has answered our prayers, we should be led to meditate upon his kindness more ardently.
And fifthly, that at the same time we embrace with greater delight those things which we acknowledge to have been obtained by prayers.
Finally, that use and experience may according to the measure of our feebleness, confirm his providence, while we understand not only that he promises never to fail us, and of his own will opens the way to call upon him at the very point of necessity, but also that he ever extends his hand to help his own, not wet-nursing them with words but defending them with present help.
From Institutes, XX.3 (Battles ed. p.852)