Go to the "azoo", visit the Botanical Gardens, museums, art galleries, go swimming (indoors or out in nicer weather), walk around the Phoenix Park (see you in 3 or 4 years) St Stephens Green, visit quirky churches, (there are loads), go to a match as a spectator (rugby, hockey, tennis, soccer, GAA, lawn-bowling,etc.), walk up the mountains or out by the sea (bracing), go to a play, a concert, go 10-pin bowling, buy a three piece suite in matching colours, buy a huge colour television, get a life, but don't get locked, stoned or high, walk around Dublin (start on the south side) and find all the houses / sites / monuments within 200 meters of the Grand Canal with literary or historic connections, award yourself another day out for each one you find, stay away from Temple Vomit (just barely south side), go to an auction, farmer's market, car boot sale, garden fete.
If all that fails, move back to Cork