How do I start doing stuff and see it till the end?

I'm and always had been a half-assed person, I never did everything till the end, wow this seems like one of those commercial, I do stuff with all energy at start then it fades out and the end comes out as a disaster, my school life just went like that.. now I'm in college nothing is working well, should I just stop doing it, I don't wanna waste my parent's money, I wanna try something new, I'm afraid it won't work, I can't do things If it arises suddenly, I never avoided problems I couldn't runfrom it so my only choice was facing it zmme what shou I do..

How do I start doing stuff and see it till the end?
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