I was where you were last year. My exact words when I went in were, "Bless me Father I have sinned. It’s been 10 years since my last confession. I think I’m going to have an anxiety attack. It went a lot better than I was expecting, considering I wasn’t exactly living a life of virtue.
When doing a confession such as what you’re doing, it’s advisable to avoid venial sins for the time being, and just focus on mortal sins. I also advise writing them down. It makes it a lot easier. You don’t have to worry about your mind going blank, and if you’re nervous/anxious you can just read off your list. I also advise taking a copy or writing down the Act of Contrition just in case there isn’t one in the Confessional for you to read off of.
With regards to confessing your actual sins and making a good Confession you should make sure you give your state in life (ie: I’m a 33 year old married woman) so the priest has an idea of the soul he’s dealing with. Plus your state in life can change the gravity of your sin and/or cause additional sins (ie: Committing adultery is also the sin of sacrilege because you’re violating your marriage vows.). This is done after you say your little “Bless me Father” intro.
With regards to how to confess sins, mortal sins must be confessed in both kind and species (ie: it’s not good enough to just say “sins against chastity/impurity” You must state which ones specifically.). Also, the number of times each one was committed must be confessed (ie: once, twice, every day, about once every two weeks, etc. You don’t need to get caught up or rack your brain over this. Just do the best you can.) Finally, you must also confess any circumstances which mitigate or increase gravity/culpability of the sin (Ie: You were held at gun/knife point, you have an addiction/mental health issue that contributes to your sinning such as being a kleptomaniac and having issues not stealing
or something).
Finally, once you’re done confessing, say something like “For these and all the sins of my past life I am humbly sorry and ask for penance and absolution.” Doing so let’s the priest know you’re finished, so there is not awkward silence, or he doesn’t think you’re trying to build up courage to confess some humungous mother-of-all sins.
Also, make sure when you go to Confession that you have some sorrow for your sins (the fear of going to Hell is sufficient, but because you have to suffer the consequences does not suffice), and a firm resolution not to sin again (that doesn’t mean you won’t, but don’t go in there saying you watched porn 50 times and have desire or intention to give that up. Or you’re shacked up with your girlfriend/boyfriend and have no intentions of getting separate places.)
Finally, remember, if you accidentally forget to confess a mortal sin, rest assured it was absolved indirectly by the absolution; however, if you remember it later on, you must confess it. If you intentionally try to hide or omit a mortal sin, your confession is invalid and you leave with the additional sin of sacrilege.
