From Helen Palmer's book:
3s and 7s are look-a-like. 7s have a lot of energy and work hard as long as they see are inrested in. At first glance they may look like 3s: they look for competition, are interested with victory and concerned about the reflection of their excellence in the sight of others. Even if 7s and 3s look similars from an outside point of view, they are actually driven by very different worldviews.
7s, sitting on the same bench at the forefront of Competition, are engaged in "one meaningful activity, one among many others." They also want to be highly esteemed by others, but not in a form of any power over them. They do not like to be labeled according to their profession. "To tell that I'm physicist is limitating, I am very much more than that." Their idea is to excel in many activities. "I run, I cook, I write poems, I know everything." They are less likely to reach the top, especially if it take too much time or force them to confront those who've not a good opinion about them. They want to know they have been selected to join the group of the best, but are not always willing to limit their other interests to reach the top rank. "I know I'm capable but I don't need to prove my value. " They work several days in a row to earn their money allowing them to escape, rather than to buy the car of their dreams. Proof of success is to have done a lot of fascinating things and to have reached the summit without allowing himself to be trapped by commitments.
The psychological difference between the workaholic 3 and the 7 very much more narcissistic lies in that, for 3s, their value is based on a deserved personal success. His true self may not exist, but his identity card exists. He's focused on the perfection of his work, because his value in the sight of others depends of the brilliant achievement of a task. As his reward lies not in the well-being, but the power to inspire respect from others, he works much harder than it would want.
The 7, also eager that people to have a good opinion of him, consider their own self-esteem as an accurate reflection of his inner value. He do not need to constantly make efforts because "life is beautiful and I am happy to be who I am." if others do not recognize his merits, he turned himself to seek comfort in denial and rationalizing it by saying he is not responsible for this. His ego has as many dimensions as there are ways to play. Wrong time can be erased with a walk in the countryside, a good book, a large sun, a cup of hot tea. Somehow, the 7 suffers less than the 3 from the indifference of others, because they keep company with themselves and are convinced of their bright destiny.