A PhD is a marathon, not a sprint. Or so they say, anyway.
Actually, the marathon part of your PhD is your thesis defence; a difficult and exhausting-but ultimately rewarding-challenge that lasts a few hours. The rest of it is training.
The result of your PhD marathon (and the amount of pain or elation you will feel) will depend not so much on what you do on the day, but how well you’ve prepared over the preceding months and years. It is the cumulative effect of what you do consistently over time.