IMHO, By fulfilling the actual practice, one will see these characteristics for oneself. Focus on the causes and results (seeing triple characteristics, Awakening) will follow.
It could be that merely repeating and studying (anicca, dukkha, anatta) is very limited. Much better to have direct and personal vision of it. If these are present in every mental state, then it should be seen by us when sati is developed well enough.
When someone tells "anicca", it could merely be the sound. But if one discovers it for oneself through mindfulness, then the personal knowledge is not a mere sound.
"Life is a struggle. Life will throw curveballs at you, it will humble you, it will attempt to break you down. And just when you think things are starting to look up, life will smack you back down with ruthless indifference..."