The best case is when I am (1) well-rested, (2) not hungry or thirsty and (3) not already agitated/close to being overwhelmed going into it. Socialising definitely drains me, though, and I have gotten better at recognising when I need a break before it becomes critical. That way I can politely excuse myself (if it's a social function, usually I have a plan in advance to go outside or away from people for a bit to recover).

Unfortunately it's just reality that some people are energised by that type of conversation or social interaction, whilst for others it is exhausting. Energy management is the key thing for those of us who find it draining. Interoception is sometimes impeded for individuals on the spectrum, so if it's hard to identify or keep track of how are you going (and hence whether it is time to politely exit the conversation), there are exercises one can find online to help improve interoception.