The concept of dialectics means that an experience can be both helpful and unhelpful, or two different points of view can both have elements of “truth”. So, for example, self-harm can be both helpful in that it brings a person immediate relief and is a way of coping with pain, and it can also be unhelpful in that it brings with it a variety of undesired consequences, including increased scrutiny, a sense of being unable to cope, shame and scars. This also means that a family member may want someone to stop self harming because it is not good for them, and the person may want to continue because they find it helps. Both of these things can be true.
Sounds confusing? Well It can be! Especially if the two people are in a discussion and both are trying to establish who is right. It can lead to conflict, things could get heated, and one or the other person may end up feeling unheard, invalidated, angry, dejected and so on. What if the people agreed, however, that they were both right and both wrong, and worked to find a common place that allowed for difference and at the same time allowed them to move forward effectively? That sounds like a good thing. That would be a dialectical solution.
Where it gets really interesting and indeed helpful is when people apply these ideas to themselves. How often do people try to work out whether they are right wrong, good or bad, smart of dumb, and so on. Applying a dialectical approach means letting go of this kind of stuff, accepting there may be truth in both views, letting go of the struggles these types of dilemmas cause, and trying to find a view that allows you to be effective in finding a way forward. It may sound easy but taking this view is very challenging at fist as it involves finding a whole new way of doing things. However, with practice it is a skill that anyone can develop.