So you've spent at least a few weeks, hopefully months, ideally years learning about how your ass is an erogenous zone and how anal play and anal sex can be part of an extremely satisfying sexaul experience.
You've spent the last few minutes, hopefully more getting arroused with your partner, hopefully you've had at least one orgasm, your ass is warmed up and you've stretched well with fingers and toys and now you're ready for his cock.
Now, when you're horned up and the momentum is in play, is the easiest time to forget safety. But please give thought to safe sex when engaging in anal because this act, delicious though it can be, is also riskier than both oral and vaginal sex by a significant factor.
Anal Sex is Risky
You might think of your vagina as petite and fragile but she's more capable than many give her credit for. She's beautiful, sexy, and when arroused, a full figured icon of sensuality but she's also tough. She can endure a marathon of fucking happily because she has the resources she needs. She lubricates to stop the friction causing injury and she expands to accept cocks that are unnecessarily large. She's made for sex.
Your asshole on the other hand, isn't. Don't get me wrong - it does it's job well. Dealing with that part of sustenance we don't want to deal with and on a regular basis too. For your whole life. It's a workhorse. But it's a workhorse built for a purpose - shitting. The nerves of the anus we can hack for sexual pleasure and we can engage in anal sex but we have to be careful because, if you read the fine print, the warantee doesn't cover damage caused by improper use, fun as it may be.
Up past your asshole, the anal canal interior is a very sensitive soft tissue that is much more prone to tearing, scratching and injury than your vagina walls. Unlike your vagina, your asshole doesn't secrete sexual fluid when you're arroused to help penetration glide a little smoother. Small scratches and other minor injuries are much more likely.
A small scratch, even one you can't feel inside your ass, is an opening for blood transerrable illnesses. If a man cums in your ass that has an open scratch, an illness he has can infect you through that scratch. We're talking about STI/STDs.
Not only does anal sex expose you to a higher chance of contracting sexually transmitted infections, it also exposes the owner of the penis to greater chances of problems compared to vaginal sex.
Urinary tract infections are the main problem for men. In a completely healthy couple, unprotected anal sex can result in a UTI for the man.
No one likes them but if you are with a short term partner they are essential. When you are not in a long term monogomous with someone, vaginal sex without a condom is risking your health badly enough but having anal sex without a condom your risk of contracting an STI (which the man may not even know he has) is about 20 times as high.
Condoms should always be used with lubricant and that goes double for anal sex. Condoms tend to make lube dry up faster than normal so apply then re-apply.
Even if you are in a long term and monogomous sexual relationship there is a chance of him getting a bacterial urinary tract infection from anal sex so condoms are still advisable for your heatlth, even when you are both healthy and STI free.