A fountain pen asks for a little patience and gives back a lot of comfort. Start with a fine nib, a bottle of ink in a colour you like, and paper that does not let the ink bleed through.
Hold the pen lightly, let the nib do the work, and write a little more slowly than usual. Rinse it with clean water every few weeks and cap it when you are not using it.
Within a week your handwriting will look like it belongs to a calmer person.