Throughout the years I have come to very clearly know and understand how toxic, pointless and exhausting worrying is. I firmly believe that we absolutely have the ability to create each day and in turn, create our lives based upon the thoughts we allow ourselves to think and from that, the emotions we feel and vibrations we put out. Thankfully I have gotten pretty good at recognizing a worried or fear-based thought instantly (they typically begin with "what if" or a feeling of anxiety) and then trying to replace it with either thinking of at least three things I'm grateful for, something I have to look forward to, or looking around and seeing all the many reasons I should be feeling joy, rather than fear.
If our thoughts, expectations and vibrations create our world AND determine what flows to us, I think it's vitally important to choose good-feeling thoughts and to do your very best to maintain your positivity at all costs. I'm not saying you can never feel sad and I certainly still have my days, but keep yourself in check and try to pivot your thoughts from negative to positive.
Remember, it's impossible to feel bad if you're thinking happy thoughts, so if you're down in the dumps... your thoughts are off!
To further reinforce my point, you can't go wrong with Buddha's words of wisdom...
"All that we are is the result of what we have thought."