That is not a problem. Many calligraphers have a totally different handwriting. When you are writing for function alone using your left brain your writing may not be very neat. It also depends on how you were taught, and many students are not taught to write correctly and this makes you feel your writing is not up to scratch. The good news is that your right brain does calligraphy. You start by learning and practicing the strokes that make up calligraphy and developing the muscle memory. Once you develop the muscle memory, you will see that everyone can do calligraphy.  Give yourself a second chance, be kind to yourself, you will be amazed! Being in your right brain also makes calligraphy extremely relaxing.