I'm not really sure about this. You can search it on google searching for solutions. You'll get different websites about this matter which are discussed elaborately.
If you are not sure about it, why did you post here? to increase your post count?
@OP there was always a problem for users in syncing up of mist wallets. A possible solution may be
1. Delete the Geth chaindata folder (
Backup before deleting it)
If you are using ubuntu, to delete chaindata folder go to rm ~/.ethereum/geth/chaindata/*
If not you can use the code and delete the chaindata
geth removedb
2. Open the wallet app, click Develop ->Sync with Light client (beta)
3. Restart the wallet and it would be fine in continuing with the syncing
Hope this helps, If my answer helped you in completing the sync lock this topic.