I would highly
recommend reading Getting Things Done (http://tinyurl.com/co8opte
). It's got a lot of business / office type lingo, but its really caught on in the programmer / hobbyist world. Essentially, it comes down to finding a system (whether it be all on paper, a variety of software or whatever) that works for you, and making yourself actively maintain it.
For me, the most helpful project management tools that I use now are:
1. Installing a local wiki on my machine to collect relevant data about each of my projects.
2. A simple task-manager to help me prioritize physical actions (what the next things to do on every project are). I have tried a few, but find myself loving Todoist. Todoist also has a great Chrome add-on that lets you view your prioritized list of actions quickly in your browser so you can pick appropriate things to do while you're already doing your web browsing and whatnot.
3. A big whiteboard. I recently moved and have not yet put one up, but having a physical system in place (away from the computer) that you can just glance at and get a feel for what you having going on is great. The added bonus is that you can remain productive even when you're tired of working on your computer - just take a short break, stand in front of your whtieboard and evaluate what you have going on and whether you need to add, update or remove anything. My whiteboard usually contains a mix of Post-Its (day-to-day things and 'don't forget's), sketches, brainstorms and an overview of all the projects I currently have.
The most important thing is to just have something
in place and to use it
. When you have a system in place that you trust, and you have dumped all of your projects, progress, to-do items, etc into it, your stress level will drop dramatically because you don't have any 'loose threads' in the back of your mind making you feel like you missed something.