I undercharged for some work – what now?

I have 2 days’ work for a new employer coming up next week.  It’s the first time I’ve done this kind of work in the country I now live in.  I quoted my normal fee, but now I feel that I undercharged for a few reasons.

1. I didn’t include the 2 travel days there and back.  They are paying my hotel and train fares, but I’m losing two days due to travel.
2. They changed what they asked of me, so I have had to effectively prepare twice for the 2 day workshop I’m running (the communication around this was confusing as the person I was dealing with left and someone else took over, so they could argue that was the reason they changed the program).
3. I’ve had to translate all my teaching materials into the language I’m teaching in (I have never taught in this language before, although I speak it).  I can’t really tell if this should cost extra as I guess they could argue that they could have just gotten a native-speaker.
4. I heard via a friend that they are very well-funded, but I charged them my community organization rate (they are a community organization).  She had done some work for them last year and had charged double what I’m charging.

I’m feeling a bit upset with myself because once I’ve paid my food for those 4 days I’m away, my 2 days pay of 500€ (250€ p/day) will be significantly reduced.  I also realized that I charged less than what I could have charged because I didn’t want to feel pressured to deliver a higher quality program, as it was my first time teaching in my non-native language.  This makes no sense as I always deliver the best of my ability no matter what.

I’m assuming that I’ll just have to take this as a learning experience, and charge more next time – but I am curious to hear coaches’ thoughts.  I’d like to still be going into this feeling optimistic and confident but the shame I feel over charging less has started to creep in.  Thoughts like, “There I go again undervaluing myself” and “She charged double, why did I charge so little?”