It is about sticking with it when a) you have a long and sequential thing to write, such as a book, b) you're in people's RSS feed or something and they expect to see stuff from you, and c) you haven't yet hit diminishing returns in writing skill.

I strongly suggest experimenting with a dialogue rather than authorship format for expressing your ideas for the time being. Many people are better debaters than they are writers, and the nature of dialogue pushes you to explore an idea more fully (before you can expect the other to accept it), gives you ready-made discussion topics and food for thought, and provides feedback in every form, all the time. For me it's been first forums, then offline journals and logs, then the occasional article here and there.

Don't feel guilty for just consuming media! It's generally good to have a proper balance of speakers and listeners. Too many people producing content often translates into too few people giving a proper reading to the content being produced. Nevertheless, it's generally good to develop your writing skill, so don't let your final interpretation of your desire to write consist of that. Pursue this activity through ways that help with your inspiration and place a smaller burden on you.