Yup, visualization is very important, although there is another part to visualizing that completes it... you gota feel good about what you are thinking/visualizing. For example, before an artwork I visualise just being very happy with the result and that no matter what it ends up looking like, it'll look great. That sets a solid foundation to giving me the drive I need to get there. So just imagine feeling amazing about the artwork that you want to create and that will start you off in the right direction.
For your second Q, nothing is impossible with your imagination. You gota go inside your head to that place you want to experience first, before signs of it will start to show up around you. What you are after is the feeling above all. The more you make an effort to try see the positive, the more opportunities you will have to see it, feel better and the better it will get. Most of us are totally blind to seeing the positive when we are negative anyway. So just choose to relax more and the rest will sort itself out