It's a complex subject but I believe we can and do, influence events by thinking about them.
However, I've found that inaction can be more effective than action and where I simply haven't had time or inclination to get around to resolving an issue/making a phone call/writing a letter, it more often than not resolves itself without any help whatsoever from me.
If I have a particularly stressful matter which threatens to dominate my thinking, I compartmentalise by setting aside 10 minutes in which to dwell on nothing else and will then resolutely repel any further thoughts on the subject until the following day's allotted session.
To my mind, self-discipline is the keyword to mindfulness. Many years of meditation have taught me that we are not our thoughts and that it is perfectly possible to remain in a mentally calm and peaceful place while observing the myriad mundane and sometimes vividly lurid imaginings which can cause unease/unhappiness/distress if we allow them to rule our minds.
I'm very sorry to learn that you're a member of the club no-one wants to join and would suggest that you avail yourself of every opportunity to try the numerous relaxation techniques/sessions that are available through the NHS/MacMillan and also give some thought to hypnotherapy. Some may consider it to be a woo too far, but I've found reiki to be of immense benefit.
I often lurk on the General Health board with a view to picking up hints and tips which I pass on to a friend who has been diagnosed with cancer and it occurs to me that the latest thread 'Tamoxigang 53' may be just the place for you to offload some of your worries/fears/doubts and have a wry chuckle in the process with the inspirational women who post there - none of whom would describe themselves as being in any way out of the ordinary, but they all are iyswim.
It must seem a double whammy that dh is undergoing his own health scare and, at times like this, the pair of you are on a metaphorical see-saw where one is up and the other dow and vice versa while there are times when you'll be perfectly balanced in terms of the support you give and derive from each other.
Do you have a holiday booked, or can you and dh escape to a luxurious hotel/country inn for a couple of nights as it often easier to think positively and make rational choices when the distractions inherent in the home environment are not in evidence?
for you, honey, and I wish you and your dh speedy and full recoveries.