Hey, speaking on your fear of ruining your painting: Try not to become too attached to the art you make because you will always (presumably) be making more. This isn't to say that you shouldn't feel proud of the work you've done, just that it's important to know when to take a step back and consider your options. That type of fear can be very paralyzing and it may prevent you from enjoying art at all if it goes unchecked. Fortunately, digital painting makes that part easier, which is why it's such an accessible medium. If you can't shake off the anxiety you can copy what you have on another layer or file, that way you'll have the original to look back on. I think you are at the point where you need to ask yourself "what can I do from here?". You've already received advice about the perspective of the head, and that's something that will probably need to be changed with the sketch. Here are some options that might help: 1. Start the painting over (With the advice you've received from the other users) 2. Start another painting ("") 3. Continue working on the painting ("") 4. Take a break and do something else, then do 1, 2, or 3, whether it be quick sketching or something not related to art at all. This way you can come back with fresh eyes. Try taking the time to write down, or what will help you remember, what does/doesn't work with your painting and the steps you took for the parts that do. This way you can try replicating your results instead of having to wade through the fear of not being able to make something you feel won't be up to par. As for the hair, it might be helpful to break it down into smaller shapes while keeping in mind the direction the hair is moving and its "plains". By discerning overall larger shapes (for example, to me the top right portion of the his head reads loosely like a pyramid) then breaking those down into even smaller shapes (his hair has a lot of strong S curves). I wish I could show you what I mean, but all I have is a mouse and a very finicky computer. Remember that even though his hair is difficult to read, it is still on a three dimensional shape. Light is hitting the top of his hair and casting shadow on the bottom. Since the lighting in this reference photo is not high contrast it might be a little difficult to discern, but it is doable. It's always okay to make mistakes and to try again, especially on a digital medium for how forgiving it is. You're doing a great job!

Fist of all, you got the color down really well (I always struggle with that). And the linework is good. One thing that helps me is double checking that individual features are in proper relation to each other and work outward from there. It seems like the eyes could be more horizontally alligned and the right side of the head is closer to the eye. Maybe check the angle of the jaw too? I've found quick sketching the same head multiple times close together helps you see what parts of your drawing look correct and which should be corrected. Each sketch will be different and you can combine the good stuff into the final drawing. Keep up the great work, though, it's looking good :)

i think there is a perspective problem: on the reference, the distance between the tip of the nose and the border of the face on the right is much smaller than on your portrait. The nose is also covering part of an eye on the reference, and this is missing in your painting. Have you tried flipping the canvas horizontally? This helps spotting that kind of problems.