I'm relatively new also and I feel the same way. I'm having trouble finding trees with good, low limbs to walk on, so I end up climbing a hickory in my backyard, whose lowest limb is just over 30' - not a great place to learn. I'm having a hard time reaching a TIP high enough to get to limbs in the 50'+.
I find I get nervous in two areas: while high up but just below the canopy, hanging in space; and when approaching within a few feet of my TIP. Being in the canopy feels safer so I find myself rushing up to the first limb to overcome the anxiety. I do a short climb (~10'), stop check everything again, then descend back to the ground. It's like a dry run and gives me confidence that I didn't overlook anything. Then I go up non-stop and keep looking up at my target the whole time. When I get on the first limb, I feel a sense of relief, like a kid in bed pretending alligators are surrounding him. Going higher doesn't seem as stressful once I'm surrounded by limbs.
On the other hand, venturing out away from the trunk is becoming a hang up I need to overcome. Also, putting weight and tension back onto my system after un-weighting it is always a bit suspenseful. I think climbing with a more experienced climber goes a long way to instilling confidence when you reach a plateau.