You got some good replies and I personally am enamored by LocalSend, it is worth checking it out.

However, there is a simple way if a) you use whatsapp and b) the devices involved have access to whatsapp.
This involves not just sending files but you can send text and whatever whatsapp supports and you'll have a history of these chats should you need to have them later again. Probably possible with other platforms but I use whatsapp so that is what I setup for information transfer to myself.
The thing you want to do is create a chat group, add a friend for a very brief moment, remove said friend again after they accepted, enjoy your private group where you can dump any and all info into and pick up from wherever you have whatsapp available. The trick is to add a friend for a couple of seconds. If you create a group you are automatically in it but you cannot use it until you add someone else, then it becomes active and use-able. The fact that you end up alone in that group does not make it unavailable again. Weird but it works.