How we cite our quotes:
Down, down I come, like glist'ring Phaeton,
Wanting the manage of unruly jades.
In the base court? Base court where kings grow base
To come at traitors' calls and do them grace. (3.3.5)
Richard has a habit of talking about his own fall from grace in a way that makes us feel sorry for him. One of Richard's gifts in this play is his ability to evoke our pity despite the fact that he spends so little time pitying others and so much time pitying himself.
The comparison to Phaeton is interesting. Phaeton famously begged to steer his more powerful father Apollo's chariot. This didn't end well – he lost control of the horses, and the sun got so close to the earth that it nearly burned. Zeus finally had to kill Phaethon with a thunderbolt. Phaeton is in some ways a perfect symbol for Richard, who keeps getting compared unfavorably to his more powerful father and grandfather, and who, like Phaeton, is overconfident and loses control of his kingdom as a result. It's unclear, however, whether Richard means the comparison this way. His emphasis on "glist'ring Phaeton" and the fact that the sun was one of his chosen symbols both suggest that Richard might just be thinking of himself as a brilliant being in decline, whose death will scorch the earth.
We at time of year
Do wound the bark, the skin of our fruit trees,
Lest, being over-proud in sap and blood,
With too much riches it confound itself. (3.4.2)
The Gardener wishes Richard had been a better "gardener" of his kingdom and that he had done to his nobles what landscapers do to their trees: prune them back and keep them in check so they don't get overgrown or, in the case of the nobles, too swollen with pride. Of course, the description of something "over-proud" of its blood and ruined by too many riches applies pretty well to Richard himself.
Would he not stumble? would he not fall down,
Since pride must have a fall, and break the neck
Of that proud man that did usurp his back? (5.5.4)
This is what Richard says after he hears that Henry Bolingbroke rode through the streets on Richard's horse. Richard feels a little betrayed that his old horse pranced through the streets like a proud show pony. Then he wonders why his horse didn't fall, since, according to the famous passage from the Bible, "Pride goeth before destruction, and an haughty spirit before a fall" (Proverbs 16.18). Translation: When you've got big head and think you're awesome, you're pretty much asking to be taken down a notch or two. Of course, we all know that this applies to Richard, not his horse.