1. You're not cut out for it. To be "cut out for it" means that you are capable of something. For instance, if someone told you that you are not cut out for baseball, this means that they believe you don't have the skill to do well at baseball. 2. Burning bridges To burn bridges is to damage relationships or accomplishments after you have moved on because you believe you will no longer need them. This could be leaving jobs on bad terms after you are offered a new and better one. Specifically, it is warning that your new job may not work out and if it doesn't you should be on good terms with your old employer so you can come back to your old job. If you left your old job poorly then you have "burned that bridge" meaning you can't go back to it. This is a reference to military tactics, where a force may burn a bridge to prevent the enemy from escaping, but then in a turn of events needs to escape themselves, but find themselves with no exit as they burnt the bridges themselves.