I've gone through this recently, and it's very difficult to overcome. I've read close to 50 books on topics like this, and some of the best advice I have gotten are from 7 Habits of Highly Effective People, Turn that ship around, Talent is Overrated, Flow, and The power of habit. These books provide mental models and frameworks that you can start using immediately to overcome this issue.
What I've found is most people look entirely at efficiency. They want to produce more with less, and this is their goal. However, this usually completely leaves out the value of the activity in question. What value is it that you contribute to open source? Do they provide a truly meaningful difference in your life currently, or are they merely passive participants that are means to an end for you? Do their values and goals match your values and goals? Chances are, if you answered yes to these, then you will not need much more motivation to give back to these groups. You will do it out of a sense of duty to your values and knowing that it will satiate a personal demand you have.
Now what can you do today without reading all of the literature in the world on the topic? Write out the eulogy you want told at your funeral 3 years from now. Seriously, turn off all distractions and think long and hard on how you want your family, friends, coworkers and connections to speak of you. Chances are through this activity you will begin to define some values that define your character. Hone in on these, and identify tasks that will relate to these values and drive them forward. Think of what single activity you can do today that will have the biggest impact on your ongoing well being, and figure out how you can turn that into a habit. After you start having small successes, you hopefully will begin rewiring yourself to start chasing personal victories as opposed to constant consumption.
What I personally found is that I tried to do things for the sake of doing things. I would create simply to share, and skip the 80% of the work that would actually provide me value. Sharing with the world is important, but if you don't go through personal growth while creating, sharing with the world becomes empty and you chase metrics and statistics. You will beginning acting out of need for validation as opposed to acting out of what's important to your values. The closer you can tie your values to your actions, the more satisfaction you'll ultimately get out of what you do. It makes it easier to prioritize tasks and see a week/month/year in the future and know that you're making the correct decision not just for present you, but future you.
There's a ton of crap advice out there on this particular topic, but there's a lot of good. If you start with the few books I listed above, note books that the authors reference and relate too. Create a list from these books on what to read next. Be ready to throw away old habits and models that no longer drive your life in the direction you want to go. Habits are reprogrammable, but the longer and deeper they're held, the more effort it will take. Most people reject this entire process because in the short term, you're more likely to be uncomfortable as things don't always work out. You may lose some productivity, or at least perceive yourself as losing productivity, but habits pay off much like compound interest. It's a long game, the payoff is built up over time. Be ready to adjust your parameters to improve the likelyhood that you meet the long term goals, but don't be afraid to see short term losses. The more legitimate experience you get, the quicker it will be for you to know when to cut your losses and move on. You can always reduce this by reaching out to people who may have been in your situation. You learn more from others failures then you do successes, so make sure you fluff their accomplishments, but don't be afraid to ask about what they "wish they knew". This is often where the real advice is.