First stage is one of relief and feeling glad to not be under pressure of being the government. This last about 3 minutes.
Then comes a feeling of emptiness and then a strange lack of purpose and direction.
After that a strange fascination with the inevitable leadership contest.
Then comes the angriness.
Then the feelings of disoerientation.
It's all so difficult. You have to defend a manfesto you've just lost an election on, the Government are getting away with murder because there is a fairly prolonged honeymoon where the new regime fascinates and interests (there's nothing the 24 hour media dislike more than things staying the same and conversely they have a lot more to report when there's a new load of personality clashes to report - like Osborn v IDS), you haven't got a leader and haven't worked out what you did wrong and what you need to conceed still less what you want to offer to the elctorate.
It all takes a certain amount of time in any case and some aspects of this can't be rushed. The Government's betrayals and mistakes are slowly catching up with them and the honeymoon will pass. The leadership election is drawing to a close. Opposition initially is to rally your own side - the electorate are still drawing some pleasure from their new government, then to engage with what's going on, to attack where necessary and finally to be an alternative government.
The job (as opposed to the art - a differnt matter) of opposition is to scrutinise and not let them get away with bad policies, in particular looking at any broken promises (rich pickings here) and to wait for the government to start looking arrogant and domineering in its approach (Nick Clegg getting there faster than might have been thought).
Of course nothing make up for the fact that a Government with a majority does things you disagree with. You can criticise but not necessarily stop them.