Don't be too scared off by the comments you have here. Most only really apply to the US. I'm assuming that you are doing a biomed PhD in the UK based on your profile, so a few tips... 1/n
That said, you will doubt it. Especially at the 3-6 month period and at ~2 years in. That is normal.
2/n
At its best, the shared adversity will create unbreakable bonds between lab members. 6/n