@ionakathryn: Focus is DIFFICULT to attain; no shit! I suggest you start a meditation practice. Meditation has been shown in various research studies to improve attention, focus and overall mental well-being. You can start with Headspace: https://www.headspace.com. They have a free track called "Take 10" which comprises of ten guided meditations, one per day. This has even been recommended by Tim Ferriss. It also seems that you might be having problems with motivation. If that's the case, I suggest you stop counting on motivation and start counting on discipline instead. Read this: http://www.wisdomination.com/screw-motivation-what-you-need-is-discipline/
Regarding the career choice between a software developer or data scientist, if you're looking for advice, I don't have any because I haven't started my career yet! I was initially traveling on the data science route but then I chose to fulfil my childhood dream of becoming a game developer, so I have now taken a detour to the development side. I believe in Cal Newport's philosophy that "skills trump passion in the quest for work you love." Basically, "be so good they can't ignore you."