Using Git in an unusual workflow topic

Hi people, this is my first post here, I think is the best place where I can discuss my programming issues. If this post isn't in the correct place, please move it and forgive my dumbness.

I'm working in some personal projects, android apps, in my house. There I have my PC with Eclipse and Git, at the end of the weekend I'm always commiting changes and uploading them to GitHub. When I go to my office, sometimes I have some spare time and I open Eclipse to start working, but of course I synchronize the GitHub repository data with my local data (in order to work with the latest changes I've made in my house), but I'm always having troubles with this action: I don't know how to discard my local old files, keep the files that haven't been modified and download the latest version of my modified files. I always end deleting the folder and cloning the repo again because I mess the files... I'm sure there is a better way.

So, I'd be delighted if you could assist me on how should I work with this feature of Git. I'd like too to take advice to improve my workflow. I've checked lots of sites and tutorials about Git but I haven't been able to get useful info to match with my workflow...

Thank you in advance :)