If you want to keep your bitcoin extra secure, use a hardware wallet like a Trezor or Ledger. I like Trezor.
A hardware wallet is basically a mini computer that is specifically designed to manage your private keys and addresses (like your desktop wallet does). However, this is the only thing the hardware wallet does, and it does not have an internet connection, so it is not vulnerable to attacks like your desktop wallet is.
A hardware wallet keeps your private keys secure even if you connect it to a virus-infected computer.
A desktop/mobile wallet (also known as a "hot wallet") is fine for day-to-day usage, but if the amount of bitcoin you hold in there is starting to make you feel uneasy, you need to get a hardware wallet.
It’s like keeping cash inside your home. You’d be comfortable leaving your day-to-day spending in the kitchen drawer, but when it comes to your life savings, you’d rather keep it inside a heavy safe. A hardware wallet is that heavy safe.
Just get a Trezor and put your mind at ease.
And keep out of my kitchen drawer.