Strategy #2: Power Words
Using pain as a mental trigger to begin focusing on your breathing is helpful, but sometimes you need more. You might consider finding some power words to use. For instance, when the ride starts hammering and you realize you'll need some strength to stay up, pull harder, climb hard, etc., you can start focusing on a word that means something to you. My favorites are: "Smooth," "power" and "attack."
I associate these words with riding strong. When I am in the saddle and trying to maintain an effort level for a duration (particularly a tempo interval), and I feel myself starting to falter, get tense or pedal inefficiently, I'll start thinking: "Smooth power." For me this triggers a reminder to focus on smooth, even, controlled breathing (that I've practiced), and for my legs to pedal in circles.
I imagine riding on a warm summer day, down a flat road, in the saddle, and pushing the pedals hard, in circles. It's one of those moments on the bike when your heart rate is high and you should be suffering, but you're not. You're moving fast -- smoothly and powerfully. This image is what I imagine and try to mimic at that moment. It's triggered by the onset of some discomfort and thinking the words: "Smooth power." Search for your own trigger words and imagery.
Strategy #3: Visualization
As you learned from the last strategy, visualization is important. Having an image of yourself riding strongly gives your mind a picture to focus on when your body wants to give into fatigue instead.
There is another image that I occasionally use when riding alone that is particularly helpful during a time trial. Ignoring the question of whether or not we have auras, let's pretend you do while on the bike. Imagining that you have an energy force around you, better yet one you can manipulate, can be useful.
During a time trial or any time you have to ride hard, imagine yourself reconfiguring your aura into a sharp knife piercing the air in front of you as you slip through it. I actually use a vision of the Princess Amidala's royal starship from "Star Wars: Episode I - The Phantom Menace." The highly polished surface cheats it way through the air and its long pointed nose cuts through the wind with little effort.