Although I usually wince at the term radical and shun it like the plague (my motto in life is based on the Buddhist adage of everything in moderation including moderation), I am somewhat intrigued by its use in this specific context and may even understand the reason behind viewing and terming it as such. That said, I still disagree with it because of its extreme and hence limited view. The problem is that it all depends on the context and the circumstances, but in a way, I would not be too opposed to a somewhat radical mode of moderation, in the sense of fully involving oneself and getting involved with the item in question while still moderating it to a certain extent.
The other reason is that acceptance is hard enough on its own, but it is often limited or conditional. In the same way, I would not necessarily disagree with the concept of unconditional love, I find that it is hard if not impossible to follow through with it. I was myself rather relieved to read and find out that the person who coined this term he himself confessed that he did not always live up to this lofty idealistic concept. It is perhaps the line between humanity and sainthood and although we aspire towards the latter, we are often pulled back to the former regardless of will and intention but out of necessity of being human and living a human life.
Yet, first things first. Why is acceptance so important and what is it that we ought to accept in the first place? I think we can set the stage with the simple basic assumption that we are not angels; we are human and with it comes all the beauty and aspirations but also all the shortcomings and weaknesses associated and connected with this fact. A human life, starting with birth, is a seed that can germinate and blossom into a range of potential states of existence and can fluctuate on the dimensions of two extreme poles, the demonic and the eudemonic or angelic side of our nature.
Since a fully lived and experienced life is not a matter of either/or nor of neither/nor, we find ourselves on a spectrum of sorts. And this is one of the most important tenets, we ought to keep in mind from the onset. We must accept that it is not clear-cut and simple but messy, gray, and complex, or what I prefer to call colorful.
Buddhism has a more pessimistic outlook or premise, namely that life is suffering. I am not denying this and accept that suffering is an inevitable part of life. It is enmeshed with it, the same way, you cannot have life without its counterpoint death or a body without a head. Each side not only defines the other but keeps it in balance where hubris would be calibrated and grounded with memento mori.
In the same way, doing good becomes useless without the existence of evil - and might I add the freedom and choice to do evil - there can be no life without death. A book that opens on the first page requires its final page for its completion, that is, to close off the story. As Aristotle would say and Shakespeare would not disagree with this, our life is like a play with a beginning, middle, and end. Each section has its own function and purpose.
To believe that we can cheat or escape death or remain young and youthful throughout our whole lives is a delusion and demonstrates a lack of acceptance if not a deficiency of reason. And yet many of us lie to ourselves and others about our age and we assume that we are immortal in this human shell of ours when we know if not consciously then unconsciously that this is far from the truth. (Please note that whether the soul can exist in the afterlife is another matter and not within the range and scope of this post, but may I direct you to a different post where the afterlife is the main topic of discussion.)
Consequently, the first pair of tenets of acceptance is that we are mortal and that life will bring with it suffering. Part of this suffering will be from external sources and part of it will be internally contingent. Some of them will be related to the facts of existence and others to the fact of being human. Some of them are just there and for everyone to see while some of them are created by ourselves and for ourselves.
In a sense, and keeping our analogies in perspective, we are moving now to stoicism. The stoic knows that they will have to face significant life events and turbulent times, but they train themselves not to be affected by them. At the heart of this approach and training lies acceptance. This diminishes and decreases levels and states of neuroticism. It is not within our reach to avoid certain facts of life. We do not linger or harbor upon how we could have done otherwise or circumvented it, but we know that it is what it is. We are not divine beings and do not have those types of superpowers (we may have other kinds though).
The serenity prayer may come to mind, and it is a life-long juggle to be able to distinguish between what we can and what we cannot control, and more importantly, knowing the intricate and inherent differences between the two. This does not mean that we are powerless in the face of life’s struggles. Au contraire, it helps us summon the strength and power to face them with magnanimity. Those aspects that we can potentially change, we have some power over, and those that we cannot, we have the power to face them stoically without feeling guilty, complaining about them, or blaming others for it all.
The stoic takes everything as it comes and does not discriminate. This is one of the superpowers we have in life, our reactions to it. Our outreach is often limited and out of reach but how we react is generally and predominantly within our reach and power. Acceptance is the first step and the step to avoid at all costs is giving up. Once you give up, you fold on life, and it is akin to death.
But as long as you are breathing, as long as the spirit moves, bounces, and rumbles within you and your body, as long as there is a spark or fire in your belly, you are alive and you can make choices, if not how to act, then how to re-act to life itself. This is the freedom no one can take away from any of us.