Yesterday I tried making a Bitcoin transaction and I accidentally added the same address it's coming out of. Mistakenly I may have tap the copy to clipboard without realizing. Luckily for me I did not click the send button before I realized my self.
You probably notice this because it was a mistake on your end and the wallet in question was not in any way similar to the one you want to send your bitcoin to, or maybe you already knew the beginning and ending of both the send-out and receiving addresses.
If it was a clipboard address that generated and changed your address to almost an identical one with the one you are sending it to, I doubt you could have been able to notice this error; it could have only been noticed after you could have waited for days without seeing the transaction in the main receiving address.
Be it a mobile wallet or trying to send from a desktop, with things that are happening currently in regard to the clipboard virus, the safest way is to use your hand and type your address one after the other to make sure that they are correct and nothing changes as a result of the copy and paste, and most times I make use of the QR code scanner to scam an address directly from the receiving side. Always don't just look at the beginning of your transactions, but always look at every bit of it to be sure they are not changed.