I have some trepidation about the term “personal practice” as it implies the notion that there is indeed a “person” who practices. We may approach practice in the beginning from just such a perspective, we have little else to go on. Most people approach the contemplative aspect of Buddhism from the perspective of “personal” or “self” development. It’s indeed spiritual materialism –  what can I get out of this for ME? There is nothing wrong with this approach, it is hardly rare, and in fact this is how the vast majority of people at the beginning stage first come into contact with Buddha Dharma.
 
We are all immersed in the clinging of ego with little clue as to the nature of the “problem.” Of course this is all we are able to do as novices on the path, despite our deluded notions to the contrary. This sort of approach is quite normal, common and widespread, hardly out of the ordinary. At first we are often motivated to search for a “path” a “practice” due to our life experience, our experience of pain, disappointment and general dissatisfaction. These “negative” experiences in life bring us to a point where we begin to feel a nebulous sensation of something being “wrong” that somehow must be “correctable.”
 
In our first steps toward the path we are all excited with the idea that we have found a “solution” to what ails us. In the beginning we delve into practice like a kid in a candy store, surrounded with mouthwatering sweets of innumerable variety. We experience great excitement; we feel that we have finally found a way to “improve ourselves”. We begin to feel giddy in this newfound joy and cannot wait to show off our new and improved “self” to others.
 
In time this initial exuberance wears off when we begin to recognize that perhaps we have deluded ourselves rather than improved ourselves. This happens time and time again. If we somehow manage to keep up with a contemplative practice through these stages we may begin to realize that what we are engaged in is not as simple as our original preconceptions dictated. We can then begin to approach practice from a saner and more stable position and not be deluded by our own thought creations into believing this or that about our practice – whether we have made “progress” whether we have “improved.”
 
Our initial exuberance has to run its natural course; there is no way we can jump ahead, the path is walked, not traversed in leaps. These are painful lessons we learn in the beginning. We learn about disappointment, we learn about spiritual ambition, we learn about spiritual arrogance. These lessons cannot be conveyed verbally or in writing, they have to be experienced directly. We learn from experience, that is the nature of “practice.”
 
In the beginning we are immersed in egocentric reality, we know nothing else. In time, with diligence, hard work and continual disappointment we may be able to begin to attain a glimpse of non-egocentric reality. To fully embrace such a perspective, to develop it as the foundation of our lives may take many years, even many decades of dedicated practice. What has been described here in a few short paragraphs is a long duration vale of pain, dissatisfaction and disappointment that takes decades to traverse.
 
In the beginning we may feel that we “have” something called a “personal practice” that involves sitting alone in formal posture every day or multiple times daily. But what’s “personal” about it?
 
The posed question seems to differentiate between “personal” and “engaged” by implication. The notion that “engaged Buddhism” involves sacrifice begs examination.
 
Engaged Buddhism is not a “flavor” of Buddhism that we can choose as if we are at a “Buddhist” ice cream counter. “I’ll have a scoop of engaged and a scoop of personal… with sprinkles please!” Engaged practice is not about “choosing” to be “engaged” or not, more likely engaged practice chooses us. It does so often despite our preferences, despite the path we may have planned out in our own heads for our spiritual journey. We might bear this in mind; that our ambitions and projections onto our “path” are most likely hindrances that will eventually have to be burned through in a long painful process.
 
In the beginning we may have some idea that we somehow “want” to be engaged Buddhists. If we are smart, we will view such ambition with a high degree of suspicion. It is very much a part of the miasma, part of the entangling briars of ego that we have to work through. Examination and questioning is never ending on this way, complacency is a stone in the road that crops up over and over again. Unless we learn to be observant, unless we pay close attention we will find ourselves wandering into states of arrogance, deluded thinking and becoming invested in maintaining some status quo.
 
Engaged practice is perhaps something that develops out of what has been called “personal practice” it is about practice for the benefit of others and the benefit of society as a whole regardless our own personal benefit. It requires a familiarity with the traps and pitfalls we encounter in contemplative practice and cannot be properly manifest without having gone through the preliminary process of gaining familiarity with our own “personal” neurosis. This is why it is important to view the practice of contemplative training as an effort in becoming familiar with and making friends with all of the elements of mind that prevent us from seeing things clearly and precisely as they are. Neurosis can be quite aptly defined as the refusal to see things clearly and precisely as they are.
 
Engaged Buddhist practice is perhaps the flower of the root of practice, it cannot exist without the root, stem and leaves that make up contemplative practice. It cannot manifest without the base elements of a firmly established plant. Engaged practice can be viewed as post-graduate work, not something we can simply jump into from the get-go. This is perhaps worth bearing in mind when we read the words “engaged Buddhism” or “engaged Zen.”
 
At the right time engagement flowers, but we cannot force its flowering. When it flowers it does so out of a genuine understanding of our nature that mandates understanding of the “nature” of “other” and the “nature” of “all others.”
 
In time with practice we develop a comprehension of the limitation of linguistic expression along with the precise use of linguistic expression in its realm. It would be counterproductive to mistake the words for the real…
 
In summation, and to answer the second part of the question, engaged Buddhism is the flowering of practice. It does not detract or enhance, it is a natural outgrowth that exhibits great beauty and enables the propagation of Buddhadharma for the benefit of all beings.