Here is why your calligraphy feels stiff and what you can do to make it flow. Your strokes may look good on paper (the shape is correct), but you still feel like the end result looks stiff. Instead of elegant, your letters look rigid, as though you are pulling them from your brush. You have reached a stage where the flow of your writing is affected by the movement of your hand.
This is a very common situation, and you have probably come across it yourself. There are many reasons why this happens, but one common thread is: too much control. When you concentrate too hard on every stroke, you tighten your grip and stiffen up your hand, causing your lines to tremble and become irregular. Of course, you need control to achieve good calligraphy, but you also need room to relax. If your hand feels cramped, your writing will not be flowing naturally.
There is another reason for this: you are writing too fast or too slowly, and neither is right. If you focus on making each stroke perfect by going too slowly, your natural flow will be lost. You need to find your own rhythm, the sweet spot that balances control with movement. When you feel comfortable, you will write more fluidly.
There is another factor that many people do not realize: rhythm. The difference between pressure on upstrokes and downstrokes is a crucial part of your lettering style, but you are also writing with a certain physical rhythm. The more you can make this consistent, the more your writing will look natural, and less mechanical.
One more tip: pay attention to the way you connect your letter strokes. Do you have to pause between strokes because you do not know where to go next? If you raise the pen from the paper, then hesitate, and then resume writing, you break the natural flow of your writing. Understanding when your hand is in motion and when it stops, will help you write more smoothly.
Lastly, many people try to force a certain style in their writing too early in their learning process. This can make writing feel strained and difficult, and they often feel unsure when they look at their progress. But remember that your style is something that evolves slowly over time and through trial and error, so you should allow yourself the time to practice and develop your own style naturally.
Flow in your calligraphy is something you achieve as a natural result of relaxation. If you are comfortable, you will find a steady rhythm. At that point, you will start to enjoy your writing more because it will become less of a chore and more of a process that you find pleasurable.