The hardest part is to start, all else follows more naturally.
Please note that all images are copyright protected and can only be used for educational and training purposes. Use an A4 or A3 sketchbook and always jot down the date of your drawing and take notes. Do each task regardless of agreeing with the subject, this will not only teach you to push through problems but you will discover in time that you make a pleasing drawing from almost any subject. Only if you have already something planned for the day to use as a motif that suits you, should you skip suggestions.
Never be overwhelmed by a subject that seems far too intricate for 10 minutes a day, all images are just indicative. So do what you can and leave each drawing unfinished if you don't have enough time and whenever you feel like, go back to it.