A cyclecomputer is a great tool for holding speeds down. If your manageable speed is 15mph, then you can check you are holding yourself down to this on the flat. I keep my gears low, then spin out to my average speed. Then I resolutely *don't* change up, even though I feel I could go faster.

The fine weather is a killer - it's so enjoyable, I'm tempted to push myself, but then I end up sore. That gets worse throughout the week, until by Friday night I'd scream if someone bumped my thigh.