As long as you encrypt and back up your wallet immediately, there is no danger. You can throw your laptop into the ocean and still recover your bitcoins as long as you have your backup and encryption password. It seems odd, but you should encrypt, then back up, and then you can safely send bitcoins to your wallet.
no i dont have a lot bitcoin yet. the only wallet i have is from blockchain. will install bitcoin core this evening.
installing bitcoin core will mean i also have a wallet.dat file along with it?
Yeah but i'd recommend getting something like Multibit HD, that one let you point to a DropBox folder so it save encrypted copy of your wallets to your cloud storage automatically. So if your computer dies, you can still easily restore your wallets.
I would not really recommend to have Bitcoin Core your spending wallet.