The metaphysical principle: «Every determination is a negation» is often considered as it meant: «Every determination gives rise to a contradiction».
In this second form, it is not difficult to see it doesn't hold, as a general principle.
A contradiction is based on a very peculiar use of negation and as we have tried to show in "Notes on negation and contradiction", there is no universal reason to assign to it a primary position, as far as everyday language is concerned.
To this, a «dialectical thinker» could object  as follow: I have no problem at all to admit that the role played by negation is various and context sensitive, the way you said it. It's obvious we can't find any reason to ascribe an outstanding place to contradiction, when things are  abstractly considered.
But it is not up to the dialectical thinker to make any decision about whether a human experience is a contradiction or not. For instance, it is Sophocles'  Antigones to represent its own reality as a torn apart experience where the «law of family» defies the «law of polis». In concrete sphere of historical facts, what we have to do with it's not a raw material we should judge and shape, but accomplished products of human intelligence where all that matters has already been selected and lived.
But focusing on a finite and determinate cultural fact, like Greek Tragedy, it's one thing, taking it as a «category» of Universal Thought and assuming that Contradiction is the engine of the whole history, i.e. what really matters to explain its (of course) dialectical development, it's another.
If we draw up a systematic view of the world and imagine it as an organism whose growing always depends on the existence of opposite parts confronting each other, we'll presuppose (otherwise it would be an a posteriori true) a general principle to pick up those situations which match it and elect them to represent the relevant steps of  the «movement of History»: we'll presuppose that every historically relevant determination gives rise to a contradiction.
[5] A «dialectical thinker» could still observe that it is a mistake to get such a principle out of its own discourse (i.e. the discourse it actually organizes or gives life to) and try to test it «in the void».
A general principle of this kind will hold if the discourse which is based on it, once it has been completely and coherently built up, holds: at beginning it seemed but a subjective view; at the end we find out it is a «concrete form».
The answer is that the par excellence discourse so far attempting to attain so large synthesis as to turn the principle into an objective true, has been the hegelian system. It is well known and many times pointed out that the hegelian system, when considered as such, isn't really free of faults, gaps or connections which are the outcome of an understanding which seems to read too much into the matter it has to do with. It therefor comes that the principle we're talking about, can be, at the present, but a subjective view and, I'd say, considering the various roles a negation can play in everyday life, maybe just an act of faith. 
Of course, there's no bar against taking such a principle as, say, a hypothesis of historiography. But if it was an hypothesis, then dialectics would be a method and that's exactly what a dialectical thinker claims it is not.