What does the bar on the bottom of the wallet displays? There is a chance that a sudden close of the wallet will corrupt your files, but after launching it again you don't need to connect to nodes and redownload everything, only the CPU works in order to rebuild the chain.
When wallet got corrupted, resync the wallet and reindex are essential things to help it fix.
Anyway, users should leave their wallets completely shut down before turn off computer to avoid unexpected corruptions.