This should have been Theresa May's pre-election, pre calling an election, personal manifesto.
1. Prepare, train, plan and behave as though your opponents are better than you.
A certain amount of dismissiveness towards Labour, the assumption that they were an electoral disaster and a walk over, didn't do the Tories any favours.
2. Treat opponents and spectators with courtesy and respect.
Jeremy Corbyn didn't go in for dishing his opponents. The same couldn't be said for the other party leaders. Guess who therefore shone out?
3. Don't try to fix something that ain't broke.
The Tories had a majority, relative popularity and support. Nothing was broken.
4. Votes of confidence usually backfire.
If you have a vision and a strategy, just do it. Mostly people who run with vision have to deal with a certain amount of unpopularity. Just let your values and vision carry you through. Do not ask for a vote of confidence. These things signal insecurity and weakness.
5. Elections like wars, are unpredictable and costly. To be avoided if at all possible. (The scriptwriters of Elizabeth 1 put these sentiments with regard to war, into her mouth.)
6. The words of Jesus, "The first shall be last, the last first" could be translated as "The winners shall be the losers, and the losers, winners."