Blackstone on Pursuit of Happiness

I find that in discussing the Declaration of Independence's "Life, Liberty and the Pursuit of Happiness" people often link it with Locke's trio of life, liberty, and property. But that doesn't really explain the "Pursuit of Happiness" part. If you read Blackstone, however, you find a likely influence:

As therefore the creator is a being, not only of infinite power, and wisdom, but also of infinite goodness, he has been pleased so to contrive the constitution and frame of humanity, that we should want no other prompter to inquire after and pursue the rule of right, but only our own self-love, that universal principle of action. For he has so intimately connected, so inseparably interwoven the laws of eternal justice with the happiness of each individual, that the latter cannot be attained but by observing the former; and, if the former be punctually obeyed, it cannot but induce the latter. In consequence of which mutual connection of justice and human felicity, he has not perplexed the law of nature with a multitude of abstracted rules and precepts, referring merely to the fitness or unfitness of things, as some have vainly surmised; but has graciously reduced the rule of obedience to this one paternal precept, "that man should pursue his own true and substantial happiness." This is the foundation of what we call ethics, or natural law. For the several articles into which it is branched in our systems, amount to no more than demonstrating, that this or that action tends to man's real happiness, and therefore very justly concluding that the performance of it is a part of the law of nature; or, on the other hand, that this or that action is destructive of man's real happiness, and therefore that the law of nature forbids it.

This law of nature, being coeval with mankind and dictated by God himself, is of course superior in obligation to any other-It is binding over all the globe in all countries, and at all times; no human laws are of any validity, if contrary to this: and such of them as are valid derive all their force, and all their authority, mediately or immediately, from this original.