Just a few additional thoughts here:
When someone wants to buy currency they do not usually buy from someone wanting to sell nor does someone wanting to sell usually sell to someone wanting to buy. Most transactions take place via market-makers (as intermediaries) whether it is in the interbank market with real money or via brokers or even in a high street foreign exchange shop.
And these market-makers do not care whether you buy or sell, they just quote a bid/offer. That is their function. However, their bid/offer is not fixed, it reacts to the business they are getting. If the majority of customers are buying on their offers then they raise their bid/offer. Alternatively, if their bids are getting hit then they will drop their bid/offer.
Naturally, these market.makers need to offset their positions as they go and they are just as active between themselves in the interbank market, hitting each others’ bid/offers to lock in their spread profits and thereby maintaining a unity in prices, and price movements, throughout the market.
Another factor to consider is that not all deals are purely forex speculation. A huge amount relates to international trade. For example, if an international wholesaler buys goods from China priced in USD and for sell in Euros in the EU then he will know what EURUSD rate will allow him to buy the goods and sell them in his market with a mark-up profit.
The same applies to commodities like Oil and Gold which are generally priced in USD. Buyers and sellers of these commodities will act when exchange rates reach a level that works for them.
These trade deals are one reason why certain price levels seem to often form what we would call S/R. But they are not so precise as what we see on the charts. This is largely because the hugely wide use of TA naturally sharpens these general “zones” into lines. When enough traders identify the same lines they become magnets focusing all the limit and stop orders to the same tight area.
Another area where price movement is not entirely related to speculative trading is the vast sums of pension and investment funds which are shifted and adjusted according to their portfolio changes. These funds are like tankers and take a long time to change course. But, again, the exchange rate that triggers their action is related to the income they are seeking from their investment. If they are looking for interest rate income from foreign bonds then the forex rate is a factor in the decision making and timing.
But it is certainly true that the impact of short term speculative trading is significant because one can see it in the calmness of the markets during a major holiday session. But all this short term trading is via the various market-makers (banks and brokers) who simply push the price up or down in reaction to the pressures from the traders and from each other.
Just my thoughts…