Spell Slots in Dungeons and Dragons are a valuable resource, and can be used to great effect in combat. If you find that you have lost spell slots, there are a few things that you can do to regain them.
First, make sure that you are using the right spells. If you are not using the spells that you are supposed to be using, then your spell slots will not be used effectively.
Second, try to use your spell slots as efficiently as possible. This means casting the spells that will have the most impact on your opponent.
for example, casting fireball on a group of enemies will deal more damage than casting it on one individual enemy.
Finally, make sure that you are conserving your spell slots. This means using them only when they will have the most impact on your opponent.
For example, if you have a spell slot available that can cast cure wounds, try to use it instead of casting heal on an ally every time they take damage.