I've too felt this way and one of the reasons for this is you're lacking something on which you can't really put a finger on just yet.

Take this test (1) - it's from a book called your best year ever (no affiliation just found it on gr) and though it feels a little pop-pschy it does give you some insight on where you may be lacking and the cause of such feelings.

(1) https://assessments.michaelhyatt.com/lifescore/ (it will ask you for email so use mailinator)