What is true is Holy Spirit's reality. It is all based on truth. Truth means, it is actually real. Factual reality. Perfect honesty and clarity. A truth that is so permanent and absolute that nobody can change it, because God put it in place.
Down below this, in the battlefield, aka 'level 1' or the ego world or the physical universe, it's all about not-truth. Another word for that is 'false'.
In falsety, there is no actual reality, no facts, and nothing is really happening. In falsety, there is only lies, deception, illusion, deceit and distraction away from truth. This 'level' of the ego is a withdrawal away from God and away from truth, attempting to be its opposite.
So down here in the ego's world we're commonly dealing with illusions, lies and deceptions. We're lost in separation, duality, unreality. Things seem to happen which aren't really happening. Problems seem to appear out of nowhere which aren't even really problems. Our vision becomes fixated on form/matter - "the form of error", since all of it is error - untruth, falsety.
So now really your entire 'spiritual path' can be summarized quite succinctly by saying, it is the transition from false to true. It is your movement away from what is false, which means everything ego, and toward truth, which is everything Holy Spirit/God.
The truth shall set you free, as in, if you access the truth you are accessing a plane of freedom. Truth is an experiential freedom. A state of being. You do not so much need to learn to accept what is false, but only to accept that it IS false, and therefore accept that "only the truth is true".
And so this takes a lot of 'sorting out' of what is actually true and what is not true. You do not get to decide what is true. This is what the Course means by "you cannot establish the curriculum". The curriculum is the subject of truth which you need to learn. You do not get to define what the truth is, that's God's job. You only get to learn it, or to decide "when you take it".
And as you're sorting out, you're mostly going to be dealing with the ego in terms of its mess and its idea of how to wake up, which is to shift around between different forms of falsety masquerading as 'more true'. It will try to become spiritual. It will try to wake up. It will try to access the truth. But it cannot. Ego cannot be truth. Ego = that which is not true. So the problem is that we are attached to the ego mindset - to the false, and we want to KEEP it by holding onto it, and take it into a state where truth exists. It cannot go there. It does not exist anywhere in truth. There is no falsety in the truth.
So it's not that we need to change - ie the ego cannot truly change from being ego. That which is false is always false. Sorry ego, you are not allowed in Heaven. But that means, YOU, what you really are, which is not the ego, but the 'decision maker', needs to decide whether to stay with the ego in ego-land, or leave the ego and go to the 'Holy Land' (in your mind, sorry Isreal but you're just a lump of dirt).
So when 'we' are trying to access the truth or wake up to the truth, to reality, 'we' think that 'we' are going to be able to take whatever it is that 'we' think 'we' are, to the truth. But this 'we' comprises the real you PLUS the ego you. Two identities, not one, but pretending to be one. And this is the main mistake we all make, trying to drag the ego along for the ride. Its sole purpose as 'the false' is to drag us away from truth, and that is all it can ever do. We need to 'separate from it' and change hands, and go be with Holy Spirit instead.
It's good to attach to and identify with Holy Spirit. Notice though that 'you' don't really get to have a separate existence. Either you're immersed in the ego's thought system or you are immersed in Holy Spirit's thought system. And each thought system has its own thoughts. Holy Spirit's thoughts come from God. So that means, either you are going to be filled with ego thoughts or God's thoughts. There are no thoughts that are 'yours' separately - that's an ego lie.
Anyway, rambling on a bit. Wake up to truth ;-) It's good for you.