Toxic thinking can be when you dwell on things you have no control over for too long and perhaps too many times a day.
The trouble is that being responsible sometimes require you to have these thoughts so you can solve your problems. You can’t just become a complete hippie, ignoring these thoughts. To an extent they must be dealt with. For me the toxic point is when it starts to bring your mood down because that really doesn’t need to happen. Do the best you can and let the rest come what may.
Toxic also means deadly and I believe negative thoughts can kill us slowly, even quickly if allowed to grow ad thrive without check. Love the ones around you, whoever they may be because families take care of their own. One way to prevent thought toxicity is to love and empower those around you. For me that means my wife and kids, as well as some close friends. Learn what the things are that give you pleasure and happiness and do them. This also is an antidote for thought toxicity. Take on things that are solutions and that don’t contribute to the toxic stuff. Slowly, you’ll find you have ways to combat it.
We all have fears, not all of us are willing to take steps to conquer them.