well.....as a newbie myself, and having loads of time on my hands ...here's my 2ps worth....

I practice every day, not for a set time - but certainly i start off for @ 45 mins... then take a break , do something else - esp if i have got stuck or my fngers hurt. then come back to it later for just a few minutes.

and its amazing how a break can help - when you pop back a couple of hours later and its just get it right , very rewarding.

yet, if it goes not so well....well take a break and come back to it.....and suddenly it will all work .

works for me