Sometimes, something is on my heart, and it nests in my brain, and to move on with my day, I have to let it out through my fingertips via keyboard or pen and paper. Today I chose keyboard. Hope you don't mind :-)
Life takes on a certain momentum (mass, direction and speed attributes). The right mental attitude is important, but let's face it, the glass is 1/2 full if you're filling it, 1/2 empty if your draining it. To change the momentum of an object requires the application of and external source of energy/force. The larger the change, the larger the energy/force required. If I remember my physics correctly, which admittedly I may not, the larger the mass and speed of the object (direction and speed attributes of the existing condition, in this metaphor), the more external energy/force that is required to make even a small change.
For a person with an undesirable character trait that is impacting their life, every piece of this is difficult; from the self-awareness to know that some part of your life or personality is taking an undesirable trajectory, to the application of the energy necessary to make a meaningful change.
What's even more difficult, IMO, is watching someone you love build an undesirable velocity in their life, knowing what an enormous task it's going to be for them to change it when they are finally ready, and that there's absolutely nothing you can do but say words they won't hear and wait for the right time, to add your energy to theirs when they have that epiphany.
I'm sure it's an experience we all share.