In need of advise for planning a 10 day trip to Spain

You do not have enough time for Tarifa and if you don't like a fast pace save Granada for another time and just stick to two cities Barcelona and Granada or Barcelona and Madrid

Anyhow this is realistic fast paced:

Barcelona May 23, 24, 25,
Fly to Granada (that is the quickest way)
Granada 26, 27
Bus/Train to Madrid
Madrid May 28, 29, 30
Train to Barcelona
Barcelona May 31

Not sure why you've used the Spanish word for Morocco and then indicated that you want to spend a day in Tarifa. Do you mean that you want to visit Tangier from Tarifa? If so, I wouldn't bother and certainly not with only 10 days to see Spain, it would be an absolute disservice to the rest of Andalucia if you skip some very good parts just to visit Tangier.

I'm not sure what the obsession is with Tangier. It's a bit like The Cotswolds (although The Cotswolds are far more attractive), it seems people feel the need to go there because seemingly everyone else does.

You don't have 10 days. You have just 8 days in Spain. Start by accepting that as a hard truth. It's a short time to go all the way to Europe - any chance you can extend your trip by (at least) a few more days?

Honestly, with just 8 days, I'd suggest you don't really have enough time to do Madrid, Granada and Barcelona. You'll have a better trip if you skip Barcelona and stick to Madrid, Granada and that region. Forget Morocco, you don't have nearly enough time and with a "day trip" there you see the very worst of it (Morocco is great, but you should save it for another trip when you can do it justice).

David has put his finger on the essential issue. You will arrive on the 23rd, probably after an overnight flight where you'll get little sleep, and you'll be jetlagged. It will take you time to get through the airport and into Barcelona to your hotel. If you are lucky, a room will be ready, but more likely, you'll just be able to drop your bags and head out for lunch. If you are like most folks, you'll be in a haze and struggle to absorb much while trying to stay awake until it's late enough to go to bed. Some of you may still be in a haze on the next day. Then you have 7 more. On the 1st, even if you have an early afternoon flight, you won't have time for much more than packing and breakfast before leaving for the airport - you should be there about 3 hours early and allow about an hour to get there.

If you really enjoy European painting, then Madrid is a good choice, with its 3 major, great art museums (allow 2 full days to see them). Otherwise most opinions are that Madrid, while interesting, is much less so than the rest of the country. You'll use a lot of time moving. Even for a flight to Granada, you need about an hour to get to the airport, 1-1.5 hours at the airport (maybe more if you are checking luggage), an hour on the plane, time to collect bags and get to the city . . . and that doesn't include packing/unpacking, checking in/out. Then it's another 1/2 day to Madrid, Barcelona, or just about anywhere else.

There are enough sights and activities in Barcelona to fill a week, and at least half a dozen day trips. You could spend a couple of nights in smaller, medieval Girona, or 3 nights in charming Valencia if you want to split your time. Girona's about an hour away by train, Valencia maybe 3 hours.

Realistically...
May 23. Arrive in Barcelona (4 nights)
May 24. Barcelona sight seeing
May 25. Barcelona sight seeing
May 26. Barcelona sight seeing
May 27. Fly to Granada (2 nights)
May 28. Visit the Alhambra
May 29. Train to Seville (3 nights)
May 30. Seville sight seeing
May 31. Day trip to Córdoba to visit the Mezquita
June 1. Connecting flight home from Seville

Or with a night in Córdoba after Granada...
May 29. Train to Córdoba (1 night)
May 30. Visit the Mezquita, then train to Seville (2 nights), and late visit to the Real Alcazar
May 31. Seville sight seeing
June 1. Connecting flight home from Seville

First, I want to thank everybody who responded and gave me a realistic and honest opinion. Unfortunately, we cannot add time to the upcoming trip, but we sure will cut it short to 2 main cities (Barcelona and Madrid) and maybe some day trips around (time-permitting). I apologize for writing Morocco in Spanish, it was very late and I was tired and I didnt realize I wrote in Spanish. I would love to visit that area (but it will be in a different trip, your suggestions are very accurate). Besides, I want to visit that area not because "everybody is going". It is much more that a trend... I just want to experience many places in the world, and that is one of them. Thank you again for your generosity! I appreciate a lot when people take the time to give a hand to another human being.

I apologize for writing Morocco in Spanish, it was very late and I was tired and I didnt realize I wrote in Spanish. I would love to visit that area (but it will be in a different trip, your suggestions are very accurate). Besides, I want to visit that area not because "everybody is going". It is much more that a trend... I just want to experience many places in the world, and that is one of them.

The problem is that Tangier is a poor representation of Morocco. A much better experience would be Marrakech or Fes, anywhere but Tangier. I honestly can't say that I felt that I was experiencing a different culture, all I was aware of was being surrounded by tourists and everyone else out to extract money from me.

When you manage it, you will love Morocco. One more place to look forward to!