Here is a good popular reading of why hedonistic ethics and politics must fail -- including modern utilitarian ethics and political thought. You can maximize pleasure, maybe; maybe you can even structure a plan that maximizes pleasure for a group of people, given a level of resources.
What you can't do is plan to maximize happiness, because it's not that kind of a thing. As Aristotle says, and rightly, happiness is an activity -- it is the particular activity of fully engaging your virtues in the pursuit of excellence. As such the question 'are you happy?' does not especially relate to the question 'how many resources do you have?', beyond a lower boundary that gives you adequate nutrition, etc., to ensure that you have the physical capacity to pursue excellence.
All virtues require developing good habits and good training, but there is also a certain amount of capacity that either is or is not inborn. By the way, the Greek word he mentions -- eudaimonia -- doesn't quite mean 'having a good guiding angel.' A daimon is not exactly an angel: it is a kind of spirit, one that the Greeks metaphorically said rode on your shoulder: that is, you couldn't see it, looking forward. Other people could see your daimon, and could tell whether it was a good one or a bad one, but not you.
There is some wisdom in this. We fail to be able to discern whether distant people are happy -- rich and famous people should be, shouldn't they? -- but we are often able to help people we know well to see that they are happier than they realized. In fact, it is in relating to others that we do discover how happy we are: what really matters is not our internal sensation of pleasure or cheerfulness, but the relationships we build with others whom we love, respect, or honor. That is the field in which we best express our virtues, and thus the field in which we are most likely to discover how happy we can really be.