How to tactfully "decommit" from projects? As a young academic recently flown from the nest, I am starting to figure out my own research interests. I now feel like I have too many, though. During a postdoc where I struggled to fit in and produce papers, I started or agreed to take part in something like 8 projects, a couple of them well outside my field, requiring the acquisition of new skills. I've tried principal-component-like analysis to prioritize projects, splitting my week up into chunks of time devoted to particular projects, and various other methods to make meaningful progress. I think, though, I really just need to decommit myself from a couple projects or push them off by six months. What is the best way to do this without building up a bad reputation and alienating future collaborators? Or will most senior folk understand the situation as the mistakes of a young buck and not take it personally?
Better to withdraw explicitly rather than just disappear. 

After you decide which are the projects that you can and must stick with, go to the leader(s) of the others - in person - and tell them you must withdraw. Tell them your "youthful enthusiasm" overcame your good sense and you are in danger of shortchanging everyone's expectations and that you value their work too much to get in the way at this time. 

A good time to be a bit honest and humble. 

But this sort of thing has to be done face to face. Email isn't going to be a good vehicle. If face to face is actually impossible it is much harder. In such cases you may want to offer, in email, say, to stay connected but to take a lesser role. That is the sort of thing that would likely come up in a personal meeting in any case. 



Note that you don't have to be a youth to have "youthful enthusiasm". See, for example: Paul McCartney age 73