Happy-Go-Lucky is assertively optimistic or aggressively pessimistic—and I could certainly surrender and write that it's both, and not be dismissed too quickly. After all, while those who set themselves against happy-go-lucky "Poppy" (Sally Hawkins in total immersion mode) are damaged at the least and pure creeps at the worst, they do not necessarily prevail: She continues to be herself, and continues to remold the world as a good place. On the other hand, her attempts to do so often seem painfully naive. In particular, the driving instructor she must deal with because her bike had been stolen is a dangerous lunatic—and not a comic one, not a Danny McBride galoot you can't find yourself able to hate, despite his self-absorbed brutishness. No, Poppy is saddled with a deeply disturbed man (played by the ever-tightly-wound Eddie Marsan, one of the many gems in the British character actor crown). But: She takes to him, she plugs away, she insists that she can be happy—and that he can, too.
I'll leave this inkblot of a movie up to you. If I must commit to some position, I'd offer that it may be a movie that wants you to reject Poppy's worldview—and then reveals exactly the world you're left with. Whether she's a fool or not, Poppy's paradise seems better than the hell she so doggedly attempts to ignore. Whether she can survive her handmade heaven is another matter.