Even if you only consider personal happiness as important, you should reflect on the quote I posted. Some temporary unhappiness and struggle may be preferable in the long run.
Only from a very narrow set of perspectives. There are many perspectives on life and for many of them a 'utility function' would seem nonsensical at best. Economics is not as all-encompassing a discipline as some people would like to make out.
Would you care to come up with such a "perspective on life"? I bet that for any actual, constructed perspective (rather than an a-priori incompatible one like "a perspective on life such that it doesn't admit a utility function") a utility function can be defined.
Just because a utility function can be defined for a given perspective doesn't mean that it automatically makes sense from within that perspective, given that defining a utility function is choosing to view things from an economic perspective and even in economics there is a difference of opinion of what that actually means, with some economists viewing it as something abstract that is only used to discuss more fundamental things and with others saying that utility functions are in themselves fundamental.
Saying that utility functions are the "what there is to life", is a bit like 42 being the answer to life, the universe and everything in the Hitchhiker's Guide to the Galaxy. What meaning you can draw depends totally on what question you are asking, or what perspective you are looking at it from.
For instance, if you are a squirrel, then an economist might be able to calculate a utility function for your behaviour, however the concept of utility functions themselves have no bearing (as far as we know) on "what there is to life" from the squirrel's perspective.
"The more we gave in, the more we complied with that kind of treatment, the more oppressive it became."