The Magners League side dominated possession but Guinness Premiership side Gloucester took the Heineken Cup spoils with some clinical finishing.
Howells said: “Gloucester were far more clinical and we made it easier for them by throwing the ball away in contact too often.
“They played very good rugby and did much more with the ball than we did at important times.
“I am very disappointed for the players because there was no lack of effort on their part.
“What we did lack, however, was composure.”
Howells added: “I am not naive enough to think that we are potential Heineken Cup winners. This team is effectively only three months old and we have realistic targets.
“As far as the remainder of this tournament is concerned, we will be taking it very seriously. We now face Leinster in Dublin and Agen at Murrayfield, so we can still have a big say in the outcome of the group.”
Gloucester coach Dean Ryan hailed the quality of his defence in the second half.
He said: “The marking and tackling was outstanding, in the last half hour especially.
“We had not been precise enough before half-time and we talked about being more direct and solid. We came to Murrayfield to play good rugby and I think we achieved that.
“The aim now is to go to France to get an equally positive result against Agen, and only then can we think about the possibility of a decider with Leinster — depending on their next result.”
Ryan Lamb kicked an early penalty to put Gloucester ahead and then converted a try from Luke Narraway.
An Ally Strokosch try and a Chris Paterson conversion cut the gap after half-time but Mike Tindall’s try, converted by Willie Walker, put the visitors back in charge.
Anthony Allen got Gloucester’s next try and Walker added the extras before Olly Morgan also crossed.
Edinburgh’s Ben Cairns bagged a late consolation score, goaled by Paterson.
Tries: Strokosch, Cairns. Cons: Paterson 2. Gloucester: Tries: Narraway, Tindall, Allen, Morgan. Cons: Lamb, Walker 3. Pens: Lamb.
Southwell, Paterson, Di Rollo, Easson, Cairns, Godman, Blair, Jacobsen, Hall, Dickinson, Mustchin, Murray, Strokosch, MacDonald, Taylor.
Dey for Di Rollo (72), Senio for Blair (60), Kelly for Hall (77), Hewett for Dickinson (68), Pringle for Mustchin (77), Callam for Taylor (50).
Balshaw, Simpson-Daniel, Tindall, Allen, Foster, Lamb, Lawson, Wood, Azam, Nieto, Bortolami, Brown, Buxton, Hazell, Narraway.
Walker for Lamb (53), Richards for Lawson (64), Califano for Wood (59), Elloway for Azam (57), Eustace for Brown (80).
C Berdos (France).