Keeping in mind impermanence, suffering and non-self If one doesn't know the notion of "impermanence, suffering and non-self", can one see it by one's self?

I know that I don't need to "force" myself to see impermanence: but do I need to keep in mind "impermanence, suffering and non-self" when practising?

EDIT: How much do i need to keep in mind "impermance..", because if it is to low, one can see it but not realise it, if it is to high, one can intellectualize it.
According to my present (non-sectarian) teacher, the way the Three Marks are to be used is not simply as dogma to be mindful of, but rather as a tool for enquiry into our psyche -- our attachments, or preconceptions.

The way to use Three Marks for enquiry into preconceptions is to try accepting one Mark at a time and see what resistance it causes.

For example, you may spend a week trying to accept the truth of impermanence with all its implications. Does it highlight the cases of you trying to solve any problem "once, completely, and forever"? Knowing that a stable state can't be realized -- does it make all your efforts seem futile? Can you get at peace with doing your best despite this futility? Keep saying "everything is temporary" and keep watching yourself in real situations. All kinds of preconceptions, imprints and deep-lying assumptions will come up. 

Similarly, spend a week applying the truth of suffering to your situations at hand. Can you see micro-suffering hiding in millisecond-level activities? Frustration of having to apply effort. Unmet expectations. Do you secretly crave for perfect ease, with reality always matching your wishes? Do you secretly hope existence can ever be effortless? Same thing here, keep telling yourself "life is suffering" with regards to real life situations and see what reaction it causes in you. Is there an area that rebels against the inescapable universal suffering? If so, that's the preconception you need to go through.

The same way, spend another week contemplating the truth of corelessness or no-I amidst real situations. If there is no "I", where do my choices are coming from now? What is the source of my thoughts now? Are my convictions and my values really mine or could this thing called "I" be an accumulations of formulas picked up over time? Am I really as all-important as I have always assumed to be? Do people really care what I do, how I do it and even whether I exist? What if free will is illusion and all my actions are predetermined? What if life is completely pointless and has no purpose and no meaning? Watch yourself as you try these thoughts on. In your mind, is accepting pointlessness of life connected with fear of ambiguity, essentially fear of taking responsibility? Is there deep-lying conviction that something you deem of value is trully of absolute importance? If so, that's your preconception, a piece of your ego, look at it carefully.

So, try each of these on for a week: "everything is temporary", "life is suffering" and "in the grand scheme of things I don't really exist, what I think is my life is just a ripple on the surface of reality" and see what comes up. When Buddhism talks about "attachments" that's what these are, now perhaps for the first time you can meet them face to face.

Eventually, the Three Marks should be fully accepted, with all their implications. Interestingly, accepting each Mark has a surprising effect, almost the opposite of what you'd expect:


Accepting Impermanence awakens you to the eternal Now.
Accepting Suffering makes suffering disappear and turns all existence into bliss.
Accepting Pointlessness aka losing self-importance gets us in touch with unconstricted creativity and the endless energy of the absolute.


Altogether, accepting Three Marks of Existence liberates us from Samsara and connects with Spontaneous Perfection of Unconditioned Nirvana.