So truly engaged people give 100% at the time. When I am at the dragstrip in the staging lanes I try to be there mentally and physically 100%--I am not thinking about the past, I am not thinking about the future, I am just making sure the dial-ins are correct and I really thinking about the "right here and now." When I am teaching and doing my best, I am really engaged with the students, I am only thinking about the class--I am well-prepared, I am really listening, and I am genuinely excited about the content. So why don't we all live more in the moment, truly engage in the activity, work hard, and give 100%?
Well, I think some people are not truly dedicated to the activity. Of course I don't give 100% when I am folding clothes, for example, but I never said I wanted to be the best clothes folder in the world! If you are not giving 100% to something, see if you really value it.
I also think people are afraid to give 100% to something they really care about (e.g., school, work, sports, etc.), because if you fail and you give 100% you don't have as many excuses. But wouldn't you rather go down trying?
And finally, I think some people don't give 100% or don't truly engage with their activities because they are just not willing to give it their all. It takes a lot of mental and physical work to be "on" and truly engaged.
So decide, do you love what you are doing? Are you truly committed to your endeavors? Are you willing to do the hard work? Are you ready to get engaged 100%?