im 33 and was in your shoes about 8 months ago. just started mountain biking and got hooked real quick. I started out on my own wanting to learn manuals wheelies etc, and did a short session with biknben mainly covering body positioning, how to lift your wheels, and cornering. I took that stuff and just rode the shit out of my bike. i did lots of the same drills that he did with us in my back yard until I was super comfortable with everything. After that I just started watching videos on how to do manuals and wheelies, bunny hop. I can now wheelie 20-30ft, manual a few feet, and bunny hop over a cinder block (the short side haha). manuals and wheelies are extremely important on the trail. I'm not saying im a great mtb rider and I'll probably never be one. However, the more i learn, the more fun I have. look up videos by skills with phil. the cornering ones REALLY helped me. i also built some skinnys in my back yard to practice that, and a small kicker ramp (sethsbikehacks) that has started to get me comfortable with leaving the ground. practice practice practice man. Do stuff at home, and every time you hit the trail make it a priority to focus on something.