On the 17th of March 1861 Italy was declared unified. The event was strangely an anti-climax, which left most, if not all political actors in Italy, disappointed by the outcome.
Mazzini, the spiritual father of the ideal of Italian reunification, was disappointed that the unification looked less that his democratic and republican ideal of equals uniting to a greater whole, but more like an expansion (or even conquer) of the rest of Italy by the (somewhat) constitutional monarchy of Savoy/Sardinia based in Turin.
Garibaldi, the person that made the unification possible in 1861 by his conquest of Sicily and Naples and his threat to attack the papal states, was even more disappointed. His successful volunteer expedition to Sicily was subjected to harassment by the police of the Kingdom of Savoy/Sardinia, while the new King of Italy - the Victorio Emmanuelle II, did not want to jeopardise his expanded kingdom in order to free the remaining areas of Italy under foreign control (Venice under the Hapsburg and Rome under the French / Pope). He died disappointed as the troops that hailed him as leader prevented him ever fulfilling his dream of revolutionary unification.
The upper class advisor around the king of Savoy, the Count conde di Cavour was also disappointed. Through foreign policy alliances and great power diplomacy the Kingdom already secured the richest areas of North Italy, and the idea that they would have to share power with the much poorer south was abhorrent. The advisor only consented to the invasion of the papal states to stop a revolutionary ,republican version of Italy to take shape and ensure the supremacy of the Kingdom of Savoy/Sardinia above the Italian peninsula - Turin remained the capital. The idea of so many persons in need in the south and the expectation that North Italians would support them was not at all what Cavour had in mind at the beginning of 1860.
The lessons of the unification are many: Italy is now is a vibrant democracy that has managed to shape one identity out of many parochial identities and it has survived through many problems, including internecine strife. Mazzini need not to have worried as his vision finally prevailed but only after the dark shadow of Fascism. Garibaldy's Italy was completed in 1871, but the nationalistic fervour fed aspirations of greatness that led to its country's ruination in 1943. The northern dominance of Cavour is still in place, and problems not resolved due to the rapidly rapid and rushed unification during 1861 still plague Italy today.
We should see that in Italy's case, as in our own efforts to unify the island of Cyprus, there needs to be compromise of beliefs and ideals by all. The positive that we can take away is that over time one can create a new national identity without needing to reject his previous, more parochial, identity. However, despite nationalism's honourable roots, the ideal needs to be checked by realistic compromise or else it can end up doing a great damage to the nation. Most positively worries that loomed large in 1861 seem very insignificant today - just 150 years after the declaration of unity. However the planning of the day of unity and beyond is essential in the smooth running the unified state, as errors and omissions can get "locked in" and thus plague new country indefinitely.
However perhaps the most important lesson is that people with strong convictions laid them aside: they also laid aside their reservations of whether unification would work and accepted that what was needed most was a great leap of faith, especially from the leading personalities of the day. Solutions need to be based on hopes and not fears, and Italy's story, which stands proudly 150 years to the day, can affirm that.