When you learn a new movement the first attempts are usually an approximation of the complete movement. As you practice it more you will gradually hone this until you can do it easily and without forcing movements.
Remember also that to get the benefit from Somatics you need to practice regularly, at least daily. Try to make it a part of your daily routine, either when you get up in the morning which sets your muscles for the day ahead, or just before you go to bed which helps the brain to remember the relaxed muscle state. Even better if you have time is to do it twice a day which speeds up results.