A picture like this I'd use a spiral blade.Keep it very tight and go very slow till you get used to the way it cuts But your doing great.I to was afraid to go over the line but it really doesn't matter unless it's the eyes.In fact do the eyes first because they are what makes or breaks a portrait.Hold the wood down firmly that way you control where the blade goes.I too again used to break blades in the corners .?reason being is the blade binds up and over heats it's self .heat is the worst thing for blades.Its hard for me to explain what to do in the corners but i cut to the corner ,then push the back side of the bladeinto the wood as it won't cut that way and make the turn from that point on or come to the corner and go into it a few time try to widen a spot so you can turn the blade with out heating it up.In no time flat you'll be a top dog here seeing your first project is way better than mine .Your doing great,take it easy,don't worry about staying dead on the line and you be fine.Keep coming back .Something new to learn everyday here Welcome friend!