In my opinion, this is not a profitable strategy, since in this way you minimize your profit, but potentially maximize your losses - if a sporting event develops against your bet, then you lose it entirely without any compensation.
Generally it is probably a bad idea to cash out your bet, because you're going to face one of two scenarios: Either the bookmaker is willing to cash you out with what is now a losing bet at pennies on the dollar (you may as well not bother, see it through to the end and write off the loss instead of getting maybe 5% back) or the bookmaker is trying to get you to cash out of a winning bet, but still offering a much lower return than you might expect to make. It can really depend on the situation, some people might be comfortable taking a win if you are say.. a corner or a yellow card away from losing. Alternatively if you bet on goals to be below 3 and it's 2 minutes left to play with zero goals in the match - you'd be almost guaranteed to win that bet regardless, so cashing out is a bad idea. There are simply two many variables to give a definitive answer, just build up your own judgement through experience.