First of all, I'm 26 as well (1978 totally rocked).
I've read a bit about the "quarter life crisis" phenomenon. The term has been used for a while, more as a joke, but it's thought of as very serious and common now. Basically, we all know of the famous mid life crisis where you wake up at 40 and freak out because you don't know what you've done with your life, don't feel like you've achieved anything, and think it's all downhill from there. Well, it's believed that same feeling is now incredibly common among the late 20's.
In part it's because our lives are far more cluttered than the generation before, and move far faster, giving us a feeling of always being behind. There's still the ever increasing pressure to achieve, and more importantly the internal pressure to 'be happy'.
Mix that with the fact that what are traditionaly the things that are signs of success and happiness for our age group are now things that occur later in life for our generation, as opposed to our parents generation (marriage, kids, home ownership etc in our 30's vs our parents generation in their 20's), or are things that have kinda changed, for example career wise the environment we work in, the people we work with, and what it is we are doing in a deeper sense all mean far more now than just simply where we are on the ladder and how much it pays.
All this is leaving us feeling unnaturaly hollow. What used to be a simple equation is now quite complicated, and doesn't have easy, traditional answers, eg "I'm not happy because all my friends are married and I'm not". Chances are very, very few of your friends are. Or "I'm not happy because my career is not going well". Maybe it is going great, maybe you are earning great money, get promoted regularly, are succeeding in the path of your choice within a great, big company, but it's hollow, it doesn't mean anything to you.
What starsgoblue suggested is actually on the money. I think it's all about finding a new way to satisfy the soul, as it's something we all dearly need. Three things are apparently on a massive increase within our age group; volunteering, travelling, and what I'd describe as 'spiritual searching' (as opposed to just 'religion').
Everyone has their own specific problems or issues at any one time in their lives, and of course they can easily be enough to drag everything else down, but always remember to put yourself first and make sure the first thing you satisfy is your own soul. So, do try and get away, just a change of environment, one where you feel you've either been able to really relax or you've taken in something new. Give something back, it will reward you greatly, and make what you do in your average day to day feel far less meaningless. Consider friendships and relationships as a time out from everything else.
People have said when they see U2 it's like a spiritual awakening.
But you might want to try praying sometime
