Time is gobbled up by so many things each day, it can drain you. Sometimes you just have to Veg-out. Forcing yourself to learn something new when your burnt takes the fun out of playing this complexed instrument. Playing the same repetitious stuff just for the sake of practice gets boring. Many new guitarists won't find the time to play or concentrate on the mechanics involved. Finger dexterity and coordination are the key to mastering those strings and you don't always have to focused on what you are playing to acheive strength and gain composition.
Try grabbing the guitar sometimes while watching the tube and just alt. pick open strings, then jump strings for a while. After that, capo a fret with your index finger while focusing on the program instead of what you are practicing. This is a great way to play by feel and train your ear to different sounds. In a short time you will feel it when you hit a sour note. Building dexterity even when your'e veggin will motivate your desire to learn new things because your picking techniques, ear and two hand coordination have moved to a higher level. Frustration comes from the mind because your fingers won't do what you you want them to. Sometimes you just have to ignore them and let your fingers do the walking like Jimi Hendrix did.