Daniel Hannan is an MEP for South-East England, and a journalist, author and broadcaster. His most recent book is How we invented Freedom and why it matters.

It was a long, dreich winter. But look outside. Feel the soil quickening beneath your feet. Hear the racket of the returning birds. See how, in these islands, every season shows to sweet perfection. Who, in such a place and at such a time, could seriously want to be elsewhere?

Quite a few people, apparently. They are especially prominent on internet comment threads and on Twitter, and their defining ethic is pessimism. How can I possibly celebrate something as frivolous as spring, they angrily demand, when we’re overrun by debt and crime and immigrants? How can I be so effete as to admire what Shakespeare calls “the shrill-gorg’d lark” when our country is falling to pieces, betrayed by a self-serving political class?

The striking thing about this attitude is that it’s a temperamental condition rather than a response to specific circumstances. On most measures, things are getting better. Remember those “Tory cuts” we kept being threatened with? Well, here they are: crime down, household bills down, deficit down, unemployment down, fuel prices down, taxes down. But if you’re determined to cling to your grievances, you’ll find a way of convincing yourself that the figures have been cooked, or that they’re a statistical blip.

Which category you’re in will depend more on your intuitions than on the data. The more we know of neuroscience and behavioural psychology, the more we learn that what we think of as our informed opinions tend to be expressions of our personalities.

A different Shakespeare, the pollster Stephan, divides the electorate into two types: drawbridge-up and drawbridge-down. Drawbridge-up voters worry that the country is going to the dogs; drawbridge-downers believe the best is yet to come. The former regard the latter as naïve, while the latter regard the former as nasty. Each lot can sometimes be right.

Now for a hard thing that needs saying. UKIP largely speaks to and for the drawbridge-uppers. On every test of opinion, its voters are more nostalgic than the mean, more convinced that calamity lies ahead, readier to disbelieve statistics suggesting improvement. By contrast, the Conservatives, being in office, know that they must convince people that life is getting better. The distinction between the two parties is at least as much attitudinal as policy-based. As Nigel Farage put it last month: “voting UKIP is a state of mind”.

Now don’t get me wrong: pessimism has its uses. It is an antidote to the utopianism that T.S. Eliot satirised as “dreaming of systems so perfect that no one will need to be good”. A guarded, even cynical, approach to human nature has informed conservative philosophy from Edmund Burke to Roger Scruton.

Drawbridges may be raised for sound reasons. Although the general trend in Britain is for people to live longer, happier, more fulfilled lives, there are patches where the statistics have moved the other way. People in those patches, frozen out of the recovery through accident of geography rather than from any personal failing, understandably mistrust upbeat data, and their ballots are worth as much as anyone else’s. Like most Conservatives, I flinched when I read Matthew Parris’s suggestion that the Tories should “turn their backs” on them.

But reflecting people’s gripes back at them will take you only so far. Voters may share your opinion that there are too many immigrants, that welfare rules are too lax, that taxes are too high, that MPs are too lordly. But that can’t be the sum of your message. You must also offer something better.

I’m thinking, not just of the coming general election, but of the In/Out referendum which I hope will follow it. If my fellow Outers focus on the things they dislike about the EU – the waste, the corruption, the lack of democracy and, of course, the open borders – our side will lose. People may very well agree with us on each of those points; but the cumulative impression is one of overwhelming negativity. If the Scottish referendum taught us anything, it’s that voters respond to cheerfulness.

If we want to carry the country to independence, we need to show that we offer a better future. We need to talk up the global opportunities beyond the EU’s restrictive customs union. We need to focus on the advantages that will flow from being able to sign bilateral trade agreements with China, India and Australia. We need use warm, internationalist, positive language – and, not least, business-friendly language: I had a go myself this week on Bloomberg news.

UKIP supporters might protest that they are doing all these things. But, if they’re honest, they’ll admit that their headline issue for the past three years has been immigration. Indeed, I’m pretty sure that I can trace the genesis of that focus to a poll published on this website in 2012 by Lord Ashcroft, which showed that immigration was a bigger issue for most UKIP voters than Europe was. Though we now take this insight for granted, it was a surprise at the time, and UKIP strategists changed tack accordingly.

But here’s the problem. As the anti-EU cause has become associated in people’s minds with hostility to immigration, it has lost ground. Sunder Katwala, Director of British Future, calls it “the Farage paradox”: the better UKIP does in the polls, the lower support for Brexit slides. This is so even though most voters understandably share UKIP’s approach to immigration: replacing unrestricted access from 27 countries with an Australian-style points-based system makes sense. But, as I say, people don’t want politicians just to echo their discontent. They want something more.

To put it bluntly, if the “Yes” campaign is talking mainly about trade and investment while the “No” campaign talks mainly about Romanians and Bulgarians, only one side sounds grown up.

So let’s make the case for national independence in optimistic language. We are the fifth-largest economy on the planet, and the fourth military power. Our trade with the EU may be in deficit and shrinking, but our trade with the rest of the world is in surplus and growing. We sell tea to China, naan bred to India, canoes to the Inuit. We are leading members of the G8 and the G20, of NATO and the Commonwealth. We lead the soft power index, with global brands from Manchester United to Wimbledon, from Harry Potter to the Duchess of Cambridge. Our language is the most widely spoken on Earth. How much bigger do we have to be, for heaven’s sake, before we’re capable of governing ourselves?