You are up for the next step in your career.
However, even very positive changes can temporarily, at times, make you feel frazzled and a bit blue. (This is very common!)
Starting any new job is a time of transition. It can be exhilarating, exciting, intimidating, overwhelming, underwhelming and disconcerting. Normally it takes three to six months in a new job until you feel comfortable with the routine and you begin to develop relationships, and start feeling more at home.
When starting a new job, it is best to observe, to absorb and to learn the company's culture before suggesting any changes. There's no doubt that positive suggestions are greatly appreciated, but not typically until you are well situated and truly understand the company's processes and the company's goals.
If you are experiencing difficulties, speak directly with your supervisor and discuss your issues and/or concerns. Most problems can be resolved if they are dealt with quickly, maturely, and before they grow out of control.