Glad to see you are someone experiencing such a confusion, it's not bad. Actually you are alliging yourslef to what you really wanted to do, what's your passion into Digital Marketing. I experience such at times too, but I follow one thumb rule which is "Never Stop Learning". I keep on learn new things, at times they help in my key areas like Email Marketing, Lead Generation, Marketing Automation, Inbound Marketing etc and at times they help me in expanding my horizon to paid marketing like Facebook ads, or SEM etc. And in whichever direction I move I come up with something more exciting then what I am currently doing. I find a new gateway open whenever I learn something new. And this is my personal experience which I am sharing.
I hope I am able to help you somewhere.