Get interested in something? That takes work tough. Research a topic for 100 hours and then see if its still good for you, if not, you know way more than your peers and it will come in handy 100%. Motivation doesnt exist for longer than a few days or without time stress. Its just a fairytale from movies. Persistence is key and leads to motivation, not the other way around. Also for example: you can study law to be lawyer for normal people and thats boring for you, so you dont do it. But you can also study law to defend weak people, change laws or go into politics. Or because you want to get rich quick or to know what crime is nearly perfect. If it is the right study you will not know if youre not working on the side for a company in that business. And youre depressed but depression doesnt make you unable to work, thats just laziness. You need to suffer and push forward each day for 8 hours. Thats how progress feels for everyone. The rest of the day you look after yourself and relax and do new fun stuff.