I'm not sure what you should do long term, but to answer your original question. Just try and get on with your life for the six weeks and look forward to seeing him after that. Plan lots of cool stuff to keep you busy and keep your mind off him. If you think work's going to be rubbish without him then take some holidays, or some sick leave!! You'll probably find that you have some time in the 6 weeks where you just end up wallowing in self pity, but if you have plenty things planned you shouldnt really have time! Good luck x