Not everyone visualizes the same way. For some it's just a sense rather than a "picture". However if you believe you can't then you won't be able to, you would have to change than belief first. Our beliefs are our reality, our truths. If you are having trouble with gaining a skill, check your beliefs to see if you have any that are contradictory to what you are trying to do. An easy way to do that is just clear your mind and then take ten minutes and write down everything that comes to mind. then cross off those that are concrete (I'm female, I have brown hair, etc.) so you just have the beliefs whether they are your own or just ones that others have told you (I'm fat, I'm pretty, I'm smart, I can..., I can't..., etc.) and then take a plain sheet of paper and draw a straight line across it with a rule or something with a straight edge. Then use a compass or bowl to make a large semi circle above the line and then a smaller one in the center. Next draw two more lines so you are dividing the semicircles into 3 equal parts with the point inside the smaller semicircle. Mark the segments light, medium, and heavy. Hold a pendulum (you can use anything that dangles and swings freely as one, a needle on thread was the first thing I ever used as a pendulum) inside the smaller semicircle (your neutral area) and then say the statement either out loud or in your mind. The pendulum will swing in the direction of how ingrained that belief is. Mark it on your list and move to the next one. Once you are done rewrite the list of beliefs by category of how ingrained they are. Look for ones that are conflicting as well as ones that have no opposition. Those without opposition, good or bad, are more powerful because they are unopposed. Consider where those beliefs came from. Then you can decided which ones you want to keep and which you don't and get rid of the ones you want gone.
Remember though, when working with the pendulum you are getting answers from your own soul, from your higher self, not from any outside source. This is important. If you look to others to tell you through the pendulum, you are inviting them to control your life. They can then manipulate you into believing whatever they want you to, even if it is not beneficial for you. If you are looking for something or someone it is your soul that is finding that information on the astral/energetic plane and relaying that information to your conscious mind.
