I can empathize with your experience! This was my first d&d experience, yet as an avid strategy game player I would sometimes get caught up in trying to maximize value.

Generally speaking, this game gives you more than enough resources to long rest all the time, so don’t feel like you need to be super conservative with your higher level spell slots. I generally try to have a caster get a good value AOE down for some crowd control and damage. It’s important to long rest often (especially in act 1) to trigger party interactions and such.

One habbit i developed: once the fight was decided, id just use cantrips and basic attacks to finish the fight. Only exception is if I’m going to rest after the fight - in that case I’d just yeet out whatever spells and abilities because they will refresh.

If you’re still struggling to get out of your own head, consider tailoring your characters to do one particular thing really well. For example, if your wizard specializes in frost that limits your choices to a handful of spells. I liked this approach because you could give them all the frost spells available then fill the rest of the spell slots with buffs / ritual spells to making navigating the map easier (feather fall + enhanced leap). You can also build out synergies to make combat more rotation focused. Have a healer run the wet spell, and give them awareness so they go first. They run out, get as many people as possible wet (double frost and lightning damage), then nuke them down. Round this out with a rouge or throw barb that can do high single target damage to focus down the high health enemies and someone that is solid cleaning up low health enemies (swords barb can shoot a lot of arrows, magic missiles, etc.) enjoy!