How do you deal with separation anxiety when it comes to childcare for your toddlers?

My daugther started her 3hrs preschool at 2.5 years old in N1 class. It's hard to let go initially as we will feel heartpain when see our child crying in school for the first few days. I was also emotionally affected initially but after she settled down in school (about 3-4days), I can see that she is enjoying herself and loves going school. My son who is 2.5 years old now and will be going to full day childcare in April. I am starting to have separation anxiety already. I try to console myself, my son will be learning things in school and enjoy himself in school. When it's time to let go, I should let my son to learn to be independent.