I restarted trying for cursive clarity with my left hand again two years ago (I am 78) and with some practice am almost to the point of readability. I am an underwriter who is still trying to NOT slant my paper. This makes for a challenge.
In grammar school in the 1940s and 50's they would not tolerate overwriting and remained suspicious of side writers . So in junior high -- tired of passing spelling tests on approximate illegibilities, I was given and Underwood portable typewriter and ribbons by my parents. But no instructions on how to keyboard the darned thing -- but I got through college and military service using the six finger method. This is funny for a writer - my career being in news, radio, television and marketing.
My scrawl at 76 when I started was more like fly specs and hen scratches than handwriting.
I looked, searched, dug and spent hours on-line trying to find solid advice. I spent way too much on used books heralded to be to be for lefties. All seemingly were turned out by righties taking pity on we few of the left handed disability. Even the Studley book was daringly light on advice that worked for me.
Then, I finally remembered that my genius middle son had similar problems in school, and invented his own very readable version of the alphabet which allowed him to be a speed demon taking notes and writing essays and notes. In some ways it crossed Elvish from the Lord of the Rings with clean block lettering.
From that remembrance I started working on my own approach to script. A bit from here, a letter or two from there -- some practice and change to make it seem uniform and it, for me, started to work.
Several friends and editors have seen my new approach and even claimed that they could read it. While I am not happy with it yet, and have lost some momentum to illness and hospital visits, I found support and help In these forums and particularly. On pen choice, how to treat nibs and feeds and with friendly correspondence, Honeybadgers has been an immense help, even though he is a righty writer with great handwriting.
Early on here I suggested a topic set for lefties, but the moderators have somewhat rightfully felt that that there is a lot to be learned from the other topics and categories here as I would search for them -- where lefties might be tempted to go only to the one category.
Today I have downloaded many alphabet examples, tried Spencerian guides, traced letters, even tried old exercises as taught years ago.Some of it has been useful, but the greatest thing I have learned is to get comfortable after learning that righties drag the nib when we have to push, Compensate for that and invent your own personal look that you find well written. Then, it is only practice, handwritten correspondence and journaling for your own satisfaction that will "make things better."
For some, this may be a tall order, but for lefties of my (and from your picture) your age too) it seems to be the only sane advice I can give that is workoing for me.