The other day I had many ungodly thoughts coming into my mind, but instead of fighting against them I was passive and ignored them. When I went to pray I felt my prayers were very weak. Once I decided to repent and fight against those thoughts, I felt strength return to me in my prayers.
One thing we must remember is anytime we allow sin to fester in our lives, we are weakening spiritually. I’m not saying we will ever be perfect, but we will grow stronger in Christ when we deal with sin and repent right away. If there are certain sins/weaknesses that you continually struggle with, pray daily for strength to overcome in those areas. In moments of temptation you can use scripture to fight it. That is how Jesus did warfare when He was being tempted by satan (Mathew 4:1-11).