Skepticism
First, there's your own inability to believe in something you haven't experienced yourself. So, get the experience! Start small, don't expect too much of yourself and pay attention to any response you get from nature.
Workaholism
Then there's the inability to sit and watch and listen. In some ways, work is easy. You can just go ahead and bulldoze your way through the problem. Listening, to yourself or to a garden, requires a certain amount of stillness and attention, a focusing of awareness outside yourself. For most of us, that requires practice.
Death
Your attitude toward death shapes your life and what is important to you. The afterlife is a mystery. What is certain is that the purely physical body of a person, a plant or an animal, is finite and will be destroyed. What is built out of water, minerals and energy will die, dissolve, vanish.
Can you accept death as you accept sprouting and budding? Can you accept the small deaths of flowers turning into unattractive seed heads? Or are you trying to pretend aging doesn't exist by cutting off the flowers as soon as they turn brown? Form is constantly changing. The life, the spirit behind it, is always the same.
Relationships do not die.
Dealing in destruction
Gardening seems to involve as much lopping and killing as it does nurturing. Is this how you want to treat your "friends?" How do we deal with this? One way is by becoming numb, refusing to acknowledge that what we destroy is alive, has value, might even be aware in ways similar to our own awareness. Another way is by trying to preserve life as much as possible. This makes gardening more difficult, and, possibly, less rewarding.
A third way is to nurture relationship and communication with whoever joins us in the garden, bug, shrub, bird, person or boulder. As these ties grow and strengthen, the necessary destruction becomes a part of the plan, an uncomfortable necessity rather than an expression of our superior wisdom and their inferior status.
Certainly, we can avoid unnecessary devastation by careful planning, but, as the ones who choose what can stay in the garden and what needs to be tossed out, we are destroyers of life. And how we take on this role can affect our relationship with the garden as a whole.