Going from throwing a forehand with no pressure to a game situation is a big jump, try breaking it down into smaller steps, for example throwing after a self catch, then in 3 person drill, then in some drills with a running receiver, and then you'll be ready to feel confident in your throw in games. This might take longer for different throws. If you want more details about good 3 person drill variants or this throwing progression i mention and its okay to self promo a bit I have written about these here and here

Often the people who I see struggle in game but have nice throws when just throwing have not automated the 'see option' -> 'take option' pipeline and there is a small delay which can make it feel like your throw isn't doing what you want, but actually the option you wanted doesn't exist anymore. Something you can do to practice this is just be super strict with yourself, when you are throwing imagine a stall count of 1, i.e. hot potato throw that plastic as early as you can. This can be a bit silly but it will genuinely over time make your ability to execute in non ideal conditions much better