Sounds simple, doesn't it? I know I'm not alone in that, while I love writing, I find it very hard to actually DO some. Once I'm going it's not hard, but those first words on the page before I've settled down are grim.
If only that were so, there'd be a lot fewer angsty writers around. I don't know a single writer who doesn't fret about their writing practice to some extent. What we do is develop strategies to get us writing - planning ahead, setting word count targets, working in spaces without internet access. Routine helps for most people, although that routine varies from writer to writer.
The only secret formula in successful writing is summarised by one 5 letter word beginning with W...
You know it. I know it. You can spend a lot of good writing time fretting about how much you really ought to be writing. You can spend a lot of good writing time reading blogs, following writers, agents and publishers on Twitter. You can spend a lot of good writing time doing the ironing or watching TV...
Writers write. That's all there is to it. I wish it wasn't like that, but there it is. To be a writer you've got to write.