First I think it's important to try and pinpoint the integral reason as to why you lack this ability to find worth in things. This is not an easy task; it requires a significant amount of self-awareness that only comes with time, lots of self-reflection and life experience. Some things that may help:
Spend time with people, go out and experience a variety of different environments and situations. Any time you find something you feel worth your attention, make a note of this and look deeper into why you care about that specific thing, whats makes it attractive to you etc.
Try teaching yourself about something, start a new hobby. Try to create something you would find hard to lose in your life. Self-improvement is highly rewarding.
Look into the science of positive thinking and mindfulness meditation. This is not a weird Buddhist teaching. It's just being mindful of where you are in the present time. Sit down, breathe and be mindful of how you are breathing, how it feels to breath, what your body feels like. You can do this with any activity by simply focussing on that one thing. This will help to bring you some peace.
Try to figure out what you want in life. Even if you may not care about it enough to implement strategies to begin achieving a goal, you need the self-awareness of what you could want.
A last note: it may be that you don't care about things due to another psychological issue. Maybe you have depression? This can lead to feelings of aimlessness and that nothing is worth caring about. Although you may find some help on Quora, this kind of question is best asked to a professional. Therapy, counselling, psychological analysis, CBT all can help.