You need to cultivate patience, if you are serious about being a writer. Sometimes, you will have days where it all seems to flow, and othertimes it will be as rough as the bottom of a parrot's cage!

If the problem is that you are not making the pace of your writing as fast as you would like, perhaps you are spending too much time on backstory or descriptions, which do tend to slow things down. Deal with backstory in dialogue. That way you won't bore yourself, or your reader. Don't use descriptive detail as filler. Every word must count.

On the other hand, maybe you are diving in to your writing, and you write at such a pace that you don't allow your writing to cook. Perhaps you expect it to be word perfect at first shot. No! Writing is about rewriting, over and over. The longer you leave your writing to cook, and then revisit it, the better. This allows you to get a much clearer idea of what you need to work on, when time and distance from your creation give you the objectivity you need. This is where patience comes in.

Strange as this may sound, it helps to take regular breaks away from writing to refuel, and get immersed in other things i.e life, which will give you ideas for what you are writing. Getting out and about gives you the opportunity to visit interesting places, or meet people, who could inspire characters and dialogue.

The time you spend asleep, may also be very productive! Keep a dream diary, and see if you can develop ideas from your dreams.

If you feel impatient because you are uninspired, you can also try using prompts. A prompt could be a piece of music, a work of art, such as a painting or photograph, it could be a souvenir, or an everyday object. You could take a line from a poem or a novel, and allow it to lead you on a journey of your own in your mind's eye.

Writing and being creative is all about helping your readers see, feel, and experience things in fresh ways. This means you should write when you feel full of energy for your passion. Try writing at different times of the day, (and night,) to discover your peak times. Keep a writing journal. Part of being a writer is about raising self-awareness, and knowing your strengths and weaknesses. Play to your strengths, and don't beat yourself up about getting it perfect first time round. Working towards perfection is enough. 

Part of professional development as a writer involves regular reading of novels and books about novel-writing.