There is no definitive truth from my experience, beyond that we do exist and nothing does not. There is that which builds and creates and that which tears apart what we are trying to create for ourselves. Relativity is so important to understand when we talk about truth. The same issue, event, or even object can appear very different to different viewers or under different light or in relativity to something else. For the same person who has trained herself to see things from more than one side, there can be choice in "truth". One hopes a trained mind would learn to choose the view that would help her create and build what she'd like.
Alas, sometimes the heart/emotions can run counter to creating the world we want. Because the heart and emotions are programmed by biology. We are driven to fit in and find mates. This is beyond our control and set by nature and this will lead many of us to make choices that run counter to creating the life we actually want. For example, stick with mates and friends who choose to tell us truths that make us feel small and tear down what we are trying to create for ourselves.
Now I say there is no truth and all is relative but of course there are lies but not all lies are meant to destroy. Some are meant to build and create a better world. But they are still lies and as such, they are meaningless and cause confusion and chaos, even still. So just because there is definitive truth does not mean we are free to lie.
I believe it is for the same reason that our skin grows thicker when we damage it, that our muscles grow stronger when we use them repeatedly, or that our skills improve when we take the time to practise them. Our identity exists, and it betrays our heart, in order to protect us from hurt and to help us adapt to the environment we are a part of so that we might live more comfortable lives - if not more joyful or fulfilling ones
I like what you said here and I think it points to an understanding that our identities and personalities are reflections of our experience and dare I say again, programming. They are not sacred and are in fact a collection of learned behaviors.
It is the mind that remains constant and is indeed nurtured by certain states of being, peaceful and curious and playful states of being, but always present and open states of being.
Compassion and rationality for example do not truly exist if they both do no exist at the same the time. They are not dualistic but work in concert if either is to be effective in enact the change you want. The seemiingly most kind and loving actions can lead to the most atrocious outcomes. Rationality makes compassion far more effective and less enabling of behaviors that chaotic and destructive.
The mind does not run contrary to the heart, rather the heart when the mind is clear and aware, guides the heart and allows the heart to enrich it. They are not at war or pulling against each other in opposite directions.The heart reflects the state of mind.