What can happen if you’re wrong? You have to rip it out and try something else. You’ve gained knowledge and lost an hour or two. Every mistake adds to your experience. As my work Project manager wrote on the white board the other day “An expert is someone who has made and learnt from every mistake that can be made in a specific area” This is the best definition of an expert I have seen. I’m not an expert knitter; I have heaps of mistakes still to be made. I can’t see that anyone could be an expert before the age of say 80.
If you look at a garment or pattern and think ‘I like that but what if….’, it is time to try breaking from the mold and doing what you want. Grab other patterns see what others have done, combine bits and pieces from different patterns. Use a completely different yarn with the appropriate needles. Give it a go and see what happens.
Most importantly relax and have fun. Mistakes and ripping it out are part of the process. The end result makes it worth it.