I seem to have difficulty performing certain feats when I am LDing such as super speed, teleportation, and shapeshifting. I try and they just seem impossible! Does anyone else have similiar issues with this? I have no problem whatsoever with flying though.
How experienced of a Lucid Dreamer are you? All of these things take willpower and patience. It may take you longer than others to get it down the first time, but by posting this problem in the first place, you are admiting to yourself you have a problem at doing it, and thus, draining your willpower to do it. All thats stopping you from doing it is you. 
TO LD4all!!!
Why not try and approach the tasks at a different angle? 
Instead of trying to make your feet run in super speed, imagine yourself moving extremely fast on a map or an overhead view. Instead of teleporting, decide that a door leads to the destination you want. Summon a mirror, and decide that you will see yourself in a different shape when you look at yourself. In a lucid dream, the imagination is the only limit 
I have had trouble with summoning really big and powerful creatures like dragons. It is as if they are “scaled down” into lesser or more well known shapes. Maybe if i imagine a picture, with a small me next to a big dragon…?
p.s. Welcome to LD4all! Please come back in chat another time!
I had these problems when I started LD’ing too and still have a piece of these problems today 
You really need to believe in yourself, I think the explanation that these problems appear is due to that you doubt too much that these powers are possible. I needed a lot of LD’s to lower this problem, my recommendation is that you have patience and a lot of LD’s 
I agree, only patience, and willpower can do it.
And about that person which asked about summoning big creatures, I think if you get familiar with the monster, it would be easier. Maybe draw a picture of it, look it, and I think that idea of putting yourself next to it. Monstrificate it, and think of it’s feats. But be careful. Sometimes, I end up either, becoming a 2 dimensional draw, or the monster turns the dream into a nightmare…
I think it all boils down to focus and imagination. Sometimes (rarely) I find myself in places where flying or traveling seems more difficult. (I believe all dreaming and LDing takes place in ‘astral’ realms, therefor, some areas we go to are more difficult than others due to the density of the place we find ourselves in)
But, when it is difficult to do something, get creative. One time I was in this place where I could not travel fast, and flying was a struggle. It was like flying through jello. So I stretched my arm and hand out at some far distant object. Once my hand was there - waaaay out there - I would let my etheric body sling towards it instead of letting my arm and hand sling back towards my body. It was a perfect way of getting around when those other travel methods are difficult.
Hehe i have trouble too. I once was in some kind of garden centre and I was standing infront of a shed for sale, I imagined that when i open the door it will be my room but when i opened it there are just a squished version of my room so it would fit inside 
yeah, willpower’s important, i’m new, so i’m still learning how to levitate and such 
I have the same problems with certain things in LDs, but I’ve found that working outside the box and finding new ways to do stuff is what helps. One time I couldn’t fly fast enough, so I imagined up a rug that would fly me faster, and it worked! And at first I couldn’t teleport in my LDs, so I convinced myself if I hop or blink, I could teleport.
Practice makes perfect