Problem can be solved with tension or without tension, just take a example where you have two roads to reach your destination, one road is smooth and the other one is spiked. I guess you'd prefer the smoother one. Now think like this the road which is smoother one is the road without tension and anyways you've to reach to the destination with in time if you'd have choose the spiked road you'd have been taking care of spikes also and that would have wasted your time. Think of it the tension is the spike, brain says you again and again "How will you do it, its impossible to do it on time!" well this distracts you and also waste your time. The road which is smoother is actually without tension and also a fast way to solve your problem.