The Hove outfit reached the semi-finals in Twenty20 and 40-over competition and missed out on the Championship trophy.
He told BBC Sport: "Having got to the stage of being in contention you'd have liked to have got over the line in one of the competitions.
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"It's a disappointment not to have got to a final. We have satisfaction with a bit of regret as well."
Sussex's bid to win the title for the first time since 2007 faltered following a rain-affected draw at Somerset last month, but Robinson is remaining positive for the future.
"At one point we had a chance of really challenging Warwickshire after a run of victories," he added.
For young players to have a taste of the pressure is invaluable for them
"We had a run of games where we had quite a few things go our way and in the last couple of weeks, we've not.
"To be honest, we're not that top of the table team really.
"We're a team that's definitely going in the right direction and that is definitely growing.
"We've made a challenge this year but in the next couple of years we'll probably be looked at as in contention."
Sussex concluded their four-day campaign with a five-wicket defeat by Durham at Chester-le-Street.
"There's not a lot that separates a lot of the teams from top to bottom in this division," Robinson said.
"The game was a nearly game for us and when we needed those big decisions to go our way, they didn't.
"We bowled a lot with a wet ball which killed us and negated us.
"However we missed a few little windows of opportunity to take the game by the scruff of the neck and Durham ran away with it in the end."
Sussex cricket manager Mark Robinson says the 2012 campaign has left him with mixed feelings.