It is a mental game and practice will bring confidence. Start small with the jumps and creep up bigger, do the same jumps over and over until you think you could do them with your eyes closed. After you are comfortable with jumping these home base jumps start to tweek a little.
Try building some small jumps over grass with gradual lips somewhere close to your house, do them often. I used to build them out of wood and drag them out for a session. Get dialed in with flat pedals and wear soccer shin guards! Put a nut guard on your top tube, like pipe insulation. Tape it on. Lower you seat. I used to wear a cup when I went big and for downhill, you can't ride long distances with one in. Jumping in clips is easier, but less forgiving.
Take your small wooden ramp to a small hill and practice landing down this slight hill (over grass). Vary you speed and gearing. You will do this so many times you will feel like the champ. Next find a small table top jump and work towards making the down landing. Table tops are great because you start small and there are no consequences for coming up short, you just land on top.
Well constructed gap jumps are hard to come up short on, like those at Blackhawk. If the gap is a bike length or so you don't have to go very fast to make it... watch a few people hit them at slow speeds and see. For now, stay away from ones with steep lips or long gaps like the one at the base of QRidge. The bigger quarry park ones can be unforgiving too, hold off on those. They aren't crazy hard, but require comitment and practice to hit. Steep lip jumps feel different than ramps.
Some where down the line you will just have a feel for hitting jumps. You will just be able to look at them and know how it will feel and how much speed will be needed. Start small and practice often.
