Inconsistency in Chess.

Okay, here's what my problem is. I am 15 years old, started playing Chess at 7, played till 11, and hadn't touched the board since then until about 6 months ago. Now I am in love with the game again, and I play on another website, and sometimes here too (you kind of get used to the board). Anyway, the thing is that I am too inconsistent. The website on which I play has a rating system like any other site. Now when I play good, I trouble even the 'big guns' of the place with a rating of over 150. But when I don't play good, I play unbelievably bad--it's like I am altogether new to the game. I overlook obvious traps, get a piece down without even noticing, and what not. In a nutshell, I play either very good or downright horrible.

Are there other members who can relate to this issue? Are there any suggestions you might provide to help my concentration (since I believe that's what the problem is)?

Everyone that plays can relate to this! My suggestions are,first, if you are playing a lot of blitz, don't. Play games where you have a couple of days to make a move and then take that time. Second, slow down. Most players with a rating of 1000 to 1200 tend to move way too fast without considering all options. And third, Study. Start with the basics. Use the training features on this and other sites to learn. Even after all of that, unless you devote hours and hours and hours to the game each day, don't expect to become a GM in this life time. Good luck, and have fun.

I do that to. I just try to think more about what my opponent can do and not just about my moves. When you do make a mistake try to think harder and see if you can get back into a good position.

Thank you for the input! Indeed, I need to consider the opponent's threat first and foremost, and only then proceed with my plan. I suppose it will come naturally with practice in games of longer time control.