From my perspective I view the term 'attachment' to signify seeking your identity in someone else or something else. If you define yourself by something that is exterior to you, and we know that every physical 'form' in this physical world is impermanent, then you would therefore stand to lose an element of your identity when these 'forms' inevitably fall away or cease to be physically present. This is what leads to the 'suffering'. If you internalize external 'things' to form your identity, when these things change form or cease to exist (on this plane), you feel like you are losing an element of yourself, and it hurts.

Example: If you don't accept or love yourself, and have a lacking inside - you may look to supplement these feelings of depravity by seeking out the love of a significant other in the form of a relationship. Things may be going great for you, and you may relish the love and acceptance that you feel from this significant other - but what happens if this individual decides to leave you, or god forbid passes away? Do you then automatically lose those feelings of love & acceptance that you identified with? Do you then lose an element of yourself or your identity and feel incomplete again? That is the inherent danger in seeking or finding 'wholeness' in someone else or something that is external to you.

You cannot control the existence of these 'things' that are external to you. Your wife or husband can leave you, your fancy sports car can get in a wreck, your mansion can burn down, your good looks can become disfigured in a horrible accident. If you seek an identity in these things you stand to lose an element of your identity when they cease to exist.

Now all this being said... I think the lesson is to find WHOLENESS and COMPLETENESS within yourself - and when I say 'yourself', I mean understanding the nature of your own consciousness. To acknowledge that you have everything you need just by the nature of your very infinite existence. You are complete & whole just as you are, with no need to define your identity with any external attachment to anyone or anything. When you come to this realization, you will end the suffering that is created by your physical mind (brain).

What often gets lost in this understanding is that it does not require you to renounce your relationships, it doesn't mean you can't be happily married or that you can't love your children. It just means that you are not using your friendships, your marriage to your significant other, or your children as the basis of forming your own identity - or for making yourself feel whole. Friendships end, marriages end, children grow up - you do not need to lose an element of yourself when this happens when you arrive at the realization that you are complete and whole just as you are and independent of the status of these friends/ wives/husbands/children. When you stop your suffering, you free yourself to love unconditionally and to full embrace your interactions and experiences that you share with others. The only difference now is that there is not a sense of 'needing' to have these things or these relationships in your life. You can certainly still enjoy them in the present moment or the NOW, but you do not have that inner need or compulsion for them nor that fear of being without them. You can embrace them and enjoy them, but you know that they do not define you and thus, if they were to change form sometime in the future, you ultimately know that you would still be whole & complete just as you exist and always have been.

I think it also ties into perspective. Is your perspective rooted in a physical existence, which we know is impermanent? Or is your perspective rooted in a spiritual existence, which we perceive to be limitless and infinite? Is your physical lifetime here the entire scope of your existence? Or is it a blink of an eye in terms of the larger nature of your existence? The more your perspective is rooted in the physical, the more vulnerable you are to suffering. The more your perspective is rooted in the spiritual, the more immune you are to suffering. I believe that energy never dies, only physical forms 'die'. When I attend a funeral these days, I don't feel any sadness for the individual who passed, but being empathetic I am likely to experience sadness for those who are still alive and suffering from the loss of their loved one. I know though, in my own consciousness, that the individual who passed is just fine, because the physical form is and always has been impermanent, and that the source of our real existence is that which cannot be harmed.

I will say though that I have never formally studied Buddhism so I did not arrive at this understanding from pursuing this ideology or school of thought in a direct sense - only from personal experience and a lifetime's worth suffering.