I don't think 'control' is the right word here. Identifying what's there, observing how your perceptions from the outside world are being processed, what leaves an impression on you and what not, and how your thoughts interact with each other is a much more realistic endeavour. Some aspects you can't even suppress properly, e.g. spontaneous feelings of like or dislike but you can investigate why they arose and where they came from. What you can control by means of consistent practice are your random involuntary thoughts in everyday life once you start empty-mind meditation or methods like mindfulness that don't involve visualisations or trance, it'll give you a much clearer idea what's really going on inside of you by shutting out the static caused by your inner dialogue.
One school of thought holds that we're all connected by a shared consciousness (a misunderstanding of Jung's archetype theory, in my opinion). I can't disprove this popular view but personally prefer to explore my own mind as if it were isolated from all the others; it's strictly self-examination I'm after. I've found it's best to keep a dispassionate, calm attitude while I'm about it - becoming all excited by one discovery, horrified by the next, ashamed by another, etc. will only cause you emotional turmoil and cloud your inner vision further.
All my efforts revolve around the question "What is really there?" Much of it means thoroughly taking stock, which could be seen as merely the first step towards self-transformation but can initiate changes all by itself. A favourite target of mine have always been narratives, stories I've been telling about myself all my life and which I tend to cling to for dear life. Some of those myths about myself proved to be particularly hard to eliminate since they've become such a major part of my identity. Self-delusion is a big issue for me, I've grown almost paranoid about it after all the stuff I've discovered. Is something true only because I want it to be true, because it's apparently based on a good storyline?
In some operations, you deliberately allow yourself to be deluded, e.g. in pathworking, but I want to know when I'm in laland and when I'm back with both feet on the ground again. Floating somewhere in between without my own volition, torn here and there by my passions without being aware of it is not my idea of occultism, and according to Gurdjieff and Buddhism, it's the default deluded state of human consciousness anyway.