"i would feel awful if my partner were reigned in by my insecurity."
Clarrykitten, please don't have any children, just yet. You are very young and you don't understand boundaries, you don't understand emotional intimacy, and you would be giving them very mixed messages.
Widen that mind. Get your head off the narrow 'casual snog' and think: 3rd party. Triangles. Energy (sexual and emotional) being DIVERTED to an EASIER no history so you can fantasise anything, stranger. Running away from problems that need solving for the easier more pleasurable flirt but the cost being closeness. Secrets and lies. Geddit?
When the person you are shagging (because clearly you are too cool to have a 'binding' relationship) is found to have been having lunch with his co-worker for months, confided in her about how unhappy he is with you, told her really private stuff about you (how your inner lips dangle outside and revolt him, say, or your stupid laugh), tells her she is the only one who understands him; and you had no idea he had this secret 'friendship' whom he defends against you,
come and tell us how that all ok and how cool you are with it all, no insecurity, like. Because, you know, they haven't touched eachother and it isn't sex.