if your visa is denied, you will probably have a right to appeal depending on the reason for refusal.
if you can provide further evidence or think the reasons for refusal were wrong you can write to the ECO manager and ask for reconsideration ( this will probably done anyway if you appeal).
or if a reconsideration doesn't work you can appeal (which could take upto 6 months or so..)
or you could re-apply paying particular attention to the reasons you were refused for last time..
most spouse/fiancée visa apps (90%+) are successful
so don't worry
