First bring into awareness the sense of "I", bring it by looking for the thinker, the presupposed intimate subject that does the thinking, the "you" that thinks.

Focus on this thinker, on this sense of "I" you have within and of yourself. Focus and try to hold your breath. You will notice that when you stop your breath, the movement of thought also stops. A thought is momentary and instantaneous, thus you have to be tremendously alert (and lucky) to happen to spot such a fleeting thought. Stopping the thinking process freezes the current thought in time and thus gives you the opportunity to more leisurely home on it, in our case, on the "I" thought, your mental image of the thinker of yourself.

Then, remember consciously that when you die, what will certainly die is this observed thinker. This intimate self of yours, your dearest identification, the ultimate object you perceive as subject, as you. This will cease to exist. Completely disappear as if it has never existed.

You might currently speculate that also you the observer will die then. You can still keep this idea, it doesn't matter as it can be only a speculation (who will be the one to observe this death?) while the death of the object, the thinker, is certain.

Contemplate on this sharp moment when this thinker will vanish. This thin border in time that beyond no thinker ever existed as there is no trace of it.

As a result, you may experience sadness and grief as if someone very dear has just died. Don't worry, this is obviously a good sign as it proves that you truly witnessed the separation of identity from the thinker. Observe and accept these feelings and move on to spot again the thinker. Or other thinker that thinks within you.