You are in control of the thought you put in your mind...
If you say you can't stop something and your heart will respond to that thought.
You simply reverse the thought.
Try it now...
Say, to yourself, I don't think about death.
Your heart will respond.
Your heart is a slave to the thought you put in your mind.
You actual heart is the inner most part of your mind.
Your physical heart only registers the thought you allow into your will.
You have one mind not two.
You choose the thoughts out of habit and if you feel some way it is because of your choices of thought you choose to believe.
I call them doctrines. If you say I am unhappy you will feel that way. Reverse that exact same logic and instantly your heart responds.
This does not work for all things (some are genetic tendencies) but it will work for thoughts of death.
I can't stop thinking about life...