Knowing what causes us to suffer (what we tell ourselves) doesn't just make the suffering stop. Neither does understanding intellectually that what happens to us is due to our own karmic actions suddenly mean we no longer get upset when we encounter difficulties.
Intellectually understanding and emotionally reacting are two very different things!
We have the habit of reacting in certain ways. So even though there's this little voice saying “Excuse me, but you're causing your own suffering!” or “This is the result of what you did in the past!” we still act out of those habits accumulated over uncountable lifetimes. And so, acting out of habit, we become angry or afraid or disappointed or whatever.
A few days, I was listening to a translation of Master Chin Kung’s talk by one of my fellow nuns. Teacher was talking about a high level of bodhisattvas who no longer had any thoughts of selfishness, greed, anger, ignorance, or arrogance. But the habit of these afflictions is still there. So even these higher level bodhisattvas still have habits. They do not act on these habits or have thoughts that arise from them, but the traces of the habits still exist.
It is little wonder then that we—beings far less advanced on the path as these bodhisattvas—still act automatically out of habit. Yes, we know but we cannot yet do. We’re still stuck in the duality of mind and heart: the mind calmly understands but the heart still blindly reacts. We have yet to reach the point where there is no separation between knowing and doing.