Example:
Turn 1: Cast haste. Do things.
Turn 2: Cast invisibility (end haste). Be invisible. No movement, no actions.
Turn 3: Be invisible. No movement, no actions. (Resolve haste)
The section on "Concentration" states:
[...] You lose Concentration on a spell if you cast another spell that requires Concentration. You can’t concentrate on two Spells at once. [...]
The haste spell states:
Casting Time: 1 action [...]
Duration: Up to 1 minute [...]
When the spell ends, the target can’t move or take actions until after its next turn, as a wave of lethargy sweeps over it.
The invisibility spell states:
Casting Time: 1 action [...]
Duration: Up to 1 hour [...]
The spell ends for a target that attacks or casts a spell. [...]
