Setting a goal equals setting myself up for failure

I bought a self-paced online course with 4 modules, recommended to complete 1 module per month. So the first month I followed recommended time frame and made sure to complete all the tasks on time. On the second module I have decided to challenge myself and complete it within 2 weeks as I believed that I can easily do it. As soon as I set this goal, I completed a week of lessons within a day and then got sort of stuck. I started to skip the time dedicated for studies, lost focus during reading time, entertain myself with thoughts creating doubt, etc. So now I am 1 week behind the schedule.

I really don’t understand what happened there. Setting a goal was supposed to drive me to achieve better and faster result. And it did inspire me for a day of massive action and then slowed me down for a week. I am not sure which thoughts created this result.

This study module is a lot more interesting than the first one. I really want to learn. More importantly this is a pattern for me: every time I set a goal to do something (even if I am already doing it), it has a negative effect on me. It’s like I am subconsiously protesting official commitment to the goal.

Should I continue to set goals and train myself to follow my plans. Or is there another way to trick my rebellious mind?