It seems to me that often temptation can come (either from the flesh, the world or the enemy) when our guard is down. This can often be when we have a break and are less under pressure to achieve things. "The devil finds work for idle hands" has some truth in it. Often after a big period of concentration or victory, we can let our guard down once the pressure is off. It is at these more relaxed times that we need to be more on guard and alert than ever.
Another way temptation works is by what can be termed "small seeds" or "the thin end of the wedge". It is often a temptation to something very very tiny or small - that seems by itself "not too bad". But this can be like a small seed that seeks to get planted. Many things in scripture begin with "seeds" rather than large things.
Similarly temptation can be like the "thin end of the wedge", for yielding to that small and tiny temptation will open the way for other bigger temptations that are like the rest of a far bigger wedge. And the wedge comes between you and your relationship with God. It is like the old saying that says "if you let the nose of the camel into your tent you will soon have the whole camel inside as well"
The good news for us is that we never need to win a "big victory" over temptation, only very small ones each time, one at a time. If we can resist a small 'suggestion' you will successfully have prevented the thin end of the wedge from gaining an entry point. We only have to win small victories in order to have bigger ones.
'Small sins' (if I can use such a phrase) can lead to 'bigger sins'. Similarly, small victories over small sins can result in greater overcoming and bigger victories over bigger sins. It is like allowing just a small hole in a ship. If you leave it for too long, the water will flood the boat, but the small hole, if dealt with, can prevent a bigger hole forming and more water entering the boat.
There is a key verse here too worth bearing in mind too in all of this:
1 Peter 2 v 11:
"Dear friends, I urge you as foreigners (pilgrims/sojourners) and exiles to abstain from sinful desires (the passions of the flesh) which wage war against your soul...."
Fleshly sinful desires that are entertained will bring about war and stress in the soul. There will be a storm within. Temptation resisted will in the end lead to peace and calmness in the soul.
May the Lord help us as we walk with Him to overcome by His grace and help and to be forgiven wherever we need it. His blood can of course cleanse. He also gives us the grace to say no to the small seeds or the small ends of the wedge.