It takes different forms, different paths for everyone. Not everyone goes down the same path. I think the best question/mindset you should start to think is this is a life with many people. You are only one piece of that puzzle, try working on your empathy first. You don't seem judgemental, but consider how others are feeling when you talk with them, listen to them more closely. Put your thoughts and replies before them, make _them_ the more important person in the conversation. (Again, not saying you are judgemental, but just in general).
Eventually, this desire to help others before yourself grows; it becomes your default response. With this, I've felt myself grow more humbler, more understanding of others and less judgemental. What you may experience is just this greater joy - helping others is giving you this happiness that nothing else gives.
At this stage, you typically start to realize bad habits you may have, distractions. We as people distract ourselves with a myriad of things in order to avoid feelings or situations. Try to uncover that, dig deep down and look at and help heal your hurts. This will likely take time and a change of behavior if you have them, but it's well worth it. Once you feel you have a good handling of this, you might start to notice others who have their own hurts. As you speak to them and gain trust with them, bring it up from time to time (if you are close), you may have an opportunity to heal them (which in of itself really makes you feel like you are doing good with your life).
If you read this, please do not be dismissive of what I am about to say, but without my belief in God - I really wouldn't know what I'm doing here. Honestly, even _in_ my belief I still very much question my purpose here on Earth. With everything else I have said up above, there was still this piece of my heart that felt like it was missing, and no matter what, nothing could fill in that gap. Point being, even though I still feel lost often, knowing and believing in God, makes me feel better that the path I'm on is on a purpose for God and for others I meet, touch, and heal along the way.
I hope this message helps you along. If you have any questions, feel free to respond.