Regarding the mental worry and tendency to ruminate over problems that so many of us suffer from, I have a useful technique I'd like to share.
At times when this tendency is driving me mad, I write down all the different problems that are going through my mind, and give them a score as to how much they are worrying me. For example, it might look like this -
(1) Car may fail MOT, how will I afford to fix it 7
(2) Ex-boyfriend hassling me with unwanted texts yet again, wish he'd leave me alone 7
(3) Friend said something hurtful, wish I could just let it go instead of thinking on it 7
(4) Computer playing up, not another thing to sort out! 5
(5) Grandad's ill again. How will I cope if he dies? 8
Then I put the list away, and after one week, I go back and re-score the items. Amazingly, it's often the case that some scores have gone down, and some items can be crossed off the list altogether! You see, in the course of a week, what seemed like the end of the world seven days ago, may now seem like nothing. So, the friend who said something hurtful has since apologised, or maybe you've realised you misunderstood him/her, or the car DIDN'T fail it's MOT after all, so panic over. Or the computer got fixed by a techno-savvy friend who didn't charge you. What it illustrates to me time after time, is how when we are in the midst of multiple worries, they all seem so bad, so difficult to cope with, but then when they are gone, we may never think of them again.
Try it and see if it helps you.