Hi Gamer
It's a common misstake to hasten yourself into details. Trying out different shading and so is OK, but try to get a whole shape together first and then go into detail.
One thing that helped me when learning to draw faces(digital) was simply just to draw onto the picture.
When I started doing oil on canvas and wanted to study a special technique I printed a copy of a painting and started to paint over it, mimicing what the artist had done.
The same thing can be done here.
Made an example of it(mainly on the left side, left the right side alone(also made it a bit smaller to not have too big areas to work with when you are not entierly familiar):

Simply use the colour from the picture and try to get a shape going.
You can also use a program to reduce the amount of colours in an image to more easily see shapes, shadows, lights etc.:

Try to study the face more profound then you will discover things like your left eye actually looks blue in this light your right eye looks green. If you can pick elements like that out you will
get a much more coherent and lifelike portrait.
So conclusion, it's really about the details on a person that makes it look like that person, it can be a mole, a wrinkle or w/e. But you have to focus on getting a solid ground to stand on just before you go into it =)
good luck
/coffee