If we can manufacture positive emotions about anything we choose, you could argue that no decision matters. No decision will make us happier (or potentially allow us to manufacture more positive emotions) than any other.
Two example goals requiring decisions:
1. Give a cool TED talk someday after becoming a professor who is super cool and respected.
2. Working at a call center job and never "progress" to any profession, but always make ends meet.
What he says is that our brain is capable of deciding to be happy with the call center job, especially if the call center becomes the only option you will ever have. Your brain is capable of manufacturing the exact same positive emotion as you would have had from being a professor who gave a cool TED talk.
If we can manufacture the same positive emotion by choosing either pathway, the question becomes: Why would anyone choose a more difficult pathway? With the knowledge that happiness can be equally felt, it seems to demotivate anyone from striving for a more stress-filled life while they could just choose to be satisfied with their call center job.
We are programmed to want something more because the process of achieving that greater self produces a greater self, whether or not the achieved self is what was imagined. We should strive for our ideal self regardless of happiness.