It's a tricky one when it comes to issues people have carrying over net form into games I reckon. The go to in situations like this is to focus on the repeatables - are you doing exactly the same thing in training as you are in a match in terms of preparation, run up, etc etc, but it might come down to you having to try to create a situation in practice that places a similar amount of pressure on you as there is in a match (or as close as possible) and then work on practicing under those conditions. Maybe you can bowl sets of overs as you would in a game, placing more importance on each delivery; or you could break your practice group up into 'teams' and create a competitive element. This is obvious, but it comes down to confidence and your ability to carry that confidence into your game. I never took practice super seriously, but I did exactly the same thing in practice as I did in a match when it came to my run up and my competition with the batsman for pretty much the whole time I was playing senior cricket. I hated going for runs and took the batsman even making contact as a small loss (which, of course, meant I had many losses), and that element was always there, whether I was practicing or playing - there was no way anyone on my team was going to get a few overs of full deliveries to practice their drives in the nets. As I said though, it's hard to give advice on carrying that mental aspect into a game, but 7-8 overs over 2 hours isn't much, so maybe start with more competitive practice and see if that helps. I wasn't overly-competitive with a lot of stuff when I was younger/throughout my cricket playing days, but I always thought I should be beating the batsmen and saw it as my job to get the best bats out, regardless of the situation. If you are good in practice, there's no reason why that shouldn't carry over into the game with a few tweaks to how you go about things.
Just out of interest, do you think you lose your action a bit/run in a bit faster/do something else a bit differently in a game to how you do things in practice? Or do you think you are just tensing up? My run-up/action was basically the same for the 10 years I was paying senior cricket, which leant a consistency to how I bowled across practice and playing. I could go into a game with very little practice beforehand and bowl ok because this was set in stone (although I may be barely able to move the next day). This obviously also removed a variable from play when it came to matches and the effect that pressure had on my performance.
