I read a great blog post, titled Don't Quit.
I came across this post through the daily post blog and I thought this is very valuable for anyone who is doing a PhD. Along the way, we encounter ups and downs, and sometimes months of effort turn out not to lead to results.
With only 1year and 4 months into my PhD, I haven't encountered a significant down yet. I've heard a lot about the famous second year dip. I, too, have come to the point were I realized that I won't be able to do everything I was planning to do at the beginning of my project. I initially wanted to take some classes and study a few new topics, but the lab is eating all my hours. However, I have not been feeling down about this, I just realized there are more urgent things that need to be done for my funding organization.
For those interested, a good read about dealing with setbacks can be found here.