This could possibly be caused by the lack of one or more of these:
Inspiration
At some stage you will become uninspired. Thankfully, this really is the easiest obstacle to overcome. The first source of inspiration comes from your competitors. Or as you should get to know them as, your peers. Within your niche, find other people writing about the same stuff you are, or similar. Subscribe to all of their feeds and organize them into a folder in your feedreader [this is particularly useful if you write multiple blogs on different subjects]. Each time you want to write and don’t have an idea of a post in mind, peruse your feeds. You won’t need to copy, you’ll get ideas yourself. The second method of gaining inspiration comes from participation. If you write a blog about golfing, go play a round of golf. Play Tiger Woods 2007 even! Take a pen and pad with you and jot down ideas you have. If you’re having trouble with something, write it down and go research it when you get home. Find the solution and write about it.
Motivation
Creatively speaking, motivation is a big deal. It’s very hard to come up with great ideas if you don’t have that drive. If you don’t want to write well, you probably won’t. This drive usually comes from regularly participating in what you write about. More importantly being paid to write and, even more importantly, providing something of use to somebody else. For now, we’ll skip the monetary aspect of blogging and focus on keeping motivation active the other two ways. The easiest way to stay motivated, as mentioned before, is to actively participate in your niche. Very similar to getting inspiration for writing about golf, getting out and playing some golf will also motivate you to write. You will also be motivated to write if you keep your audience in mind. Writing for your audience will not only improve the actual quality of writing, but also motivate you to get it started. If you think that someone else out there should know what you know, you will want to share it.
Confidence
Lack of confidence can really stifle your writing. Most of us blogging out here aren’t really experts, we’re learning as we go. Knowing that out there somewhere is another writer who probably knows more than you can make you feel like your posts are not worth writing. When you’re reading other sites’ feeds for inspiration you might begin feeling like it’s all been written – and well! Why am I even trying, it’s been done and I can’t think of anything new. This happens, but shouldn’t discourage your writing. If you don’t get any new ideas, build on an existing one. If you read an article about practicing the perfect putt, write about your experience putting with that post in mind. If you disagree, write a rebuttal. When you have something to say about someone else’s writing, and write your response, your confidence will increase. Not agreeing with someone’s writing means you have an opinion that hasn’t been discussed; and other people will have that opinion too. The bottom line with confidence, is you started this blog because you have something to say. After a few months you may have said everything you had envisioned saying when you began. Having the confidence to search for new ways of getting new ideas is important.
In Short:
If you’re running out of breath in your blog, get out there and get active. Read other posts and engage in the conversation. Talking with other readers of other sites will help develop your ideas. Participate in what you’re writing about. If you just write about it, you’ll become reliant on responding to other people’s posts. Play that round of golf and you’ll encounter new ideas for posts.