I am not sure about the answer to the second question because I am not enlightened yet. So I am not sure whether they have to be the same strength. I know they have to be very high, but whether quantitatively they have to be the same, I am not sure. According to the stories I have read in the scriptures, if one is down quite a bit and the others are excessive, this could block enlightenment. For example, Sariputta, the chief disciple of the Buddha, was known for his Wisdom. He was concerned because he was taking a longer time to get enlightened than his friend Mogallana. Mogallana got enlightened, I think, in one week or so. Sariputta was taking longer and it was kind of strange because he had a great deal of Wisdom, but apparently he was lacking in Saddha, or Confidence, and the Joy factor of Enlightenment. As he was fanning the Buddha one day while the Buddha was giving a discourse to someone else, his Saddha or Confidence in the Buddha surged. As that surged, so did the Joy factor of enlightenment, and apparently he became enlightened at that moment. So the Joy factor was a bit dry and lacking; the Wisdom was strong, and the Joy came up to balance the Wisdom. That is an interesting little story.
If we get a bit dry and lacking in Joy, we may need to change our object of meditation at that moment, to get the Joy factor up, which helps to bring up Energy as well. How can we strengthen these factors within ourselves? I have talked about Joy and reflecting on Confidence-inspiring objects of meditation. Unfortunately, we haven't the chance to fan the Buddha and listen to his discourse, so we may have to reflect about the Buddha or about Confidence-inspiring objects of meditation to get the Joy factor of enlightenment up.
Tranquility is more directed towards concentration. If we have more Investigation into Mind Objects, we can get a lot of Energy and we may go into restlessness. That is a time when we need to know how to bring about the Tranquility factor of enlightenment. That is when we may want to focus more on the breathing, in order to get the Concentration stronger so that there is more Tranquility in the mind. Then we have the power and the strength in the mind to be able to investigate more.
Mindfulness - sometimes we are not motivated to be mindful because we don't have a deeper insight into Dukkha. Things are too pleasant in our life and so we just flow along with it. Sometimes, if we are not being very aware, and are not bringing forth effort to be so, it may be helpful to reflect on Dukkha and death to get up the Energy to then bring up more effort to be mindful and have more Mindfulness of the body. Unless we have the motivation to want to do it, we don't see the value of it, especially when things are pleasant in our life. But if we realize we don't have a lot of time left and there is a lot of Dukkha, we may be more motivated to bring up the Energy to be mindful. And that is where the Energy factor of enlightenment is. The Wisdom factor helps to increase the power of Mindfulness, the motivation to be mindful.
The Seven Factors of Enlightenment connect to all the other practices that we do, the Four Foundations of Mindfulness, the Noble Eightfold Path. The Investigation factor is more the Right Understanding and Right Intention factors. How do we strengthen the Investigation factor? Wise reflection. We are not just being mindful just to be aware of things, but to understand who we are. We are observing, understanding the nature of the body and the mind. Equanimity comes from more Wisdom and seeing the three characteristics of existence and understanding that we have little power to change these things. And so we learn to be with the nature of things as they are.