Similar word to selfassurance:

accord, aplomb, assurance, balance, calm, contentment, control, cool head, cool, coolheadedness, coolness, dignity, dispassion, ease, equanimity, equilibrium, even temper, evenness, fortitude, harmony, imperturbability, inexcitability, levelheadedness, moderation, nonchalance, peace of mind, placidity, poise, polish, presence of mind, quiet, quietude, repose, sang-froid, sedateness, self-assurance, self-control, self-possession, serenity, sobriety, stability, tranquility