Mana allows dwarves to use their Healing Ale, as this is what will keep them alive in battle. Conserving Mana is vital for dwarves to fight for a long time on the battefield.
Knowing When to Heal Edit
The most basic way to conserve mana is to heal only when nessecary. If the Healing Ale is spammed, a dwarf will not survive very long in combat. It is recommended to heal when a dwarf is at half health or lower.
Getting a PROC Edit
PROCing is useful because it allows the dwarf a speed buff to escape monsters easily.
If a dwarf has the Momentum upgrade, as long as the dwarf keeps the PROC alive, the dwarf will have an Absorption shield to take incoming damage. These extra hearts will block most of the damage, and save the dwarf from using their Healing Ale while their Mana regenerates.
The PROC also allows the dwarf to instantly kill all monsters(except for Golems), so the dwarf can clear out a room.
Falling Back Edit
If a dwarf is a low on Mana, then retreating is recommended. This allows the dwarf to recover mana and repair their armor if needed. Note that if your armor is extremely low on durability, your mana regeneration will be reduced, you have to heal more often, and therefore have to retreat sooner.
If a dwarf needs to take a quick break from the battle and deal with real life, retreating is recommended.