Listening to constant complaints is a very draining experience and can frustrate the best.When you're on the move all day, physically tired,but you're doing the best you can .. and in such a situation,if all you get are complaints,you'll undoubtedly feel frustration.
Hence,Moses certainly seems to have had grounds for his complaints; the constant, exasperating complaints , his own helplessness and physical exhaustion... but of course, theoretically ,we know that complaining is not the best response to complaints.
Is this a model prayer? The Lord's Prayer is a model prayer.From that point of view this is not.But it's a very reassuring prayer for the rest of us who frequently succumb to situations and whine and complain and feel guilty about that. It's so good to know that even Moses ( or any other 'hero', for that matter) went through such situations. And God will not throw us out if we appraoch Him at times in this manner.And God did listen and give some practical solutions to Moses' problems.