My brother loves hot, spicy food, but he knows he should not eat it (I know you're out there, Chris). Before his doctor helped him deal with the problem, he would just eat those foods anyway and say something like, "I'll be sorry for this later." Long story short, he always was.
What makes us follow our instincts when we know we should not? Simple, sin dwells in us. We do not have to give into it. As Christians, we are not slaves to sin. That means when we do sin, we give in and do it anyway maybe even thinking, "I'll be sorry I did this later." Our flesh, as the Bible calls it, is a powerful force that pushes us to do what we want to do, but know we should not. Paul warns us to instead walk by the Spirit, taking our cue about what we should do from the Lord (the Holy Spirit that dwells in us).
Gal 5:16 But I say, walk by the Spirit, and you will not carry out the desire of the flesh. 17 For the flesh sets its desire against the Spirit, and the Spirit against the flesh; for these are in opposition to one another, so that you may not do the things that you please.
Paul knows what he's talking about. Even a great and spiritual man like Paul struggled against his own flesh, check it out...
Rom 7:22 For I joyfully concur with the law of God in the inner man, 23 but I see a different law in the members of my body, waging war against the law of my mind and making me a prisoner of the law of sin which is in my members. 24 Wretched man that I am! Who will set me free from the body of this death? 25 Thanks be to God through Jesus Christ our Lord! So then, on the one hand I myself with my mind am serving the law of God, but on the other, with my flesh the law of sin.
Paul essentially says earlier in the chapter, "What I shouldn't do, I do, and what I should do I don't!" Sound familiar? The struggles against what we desire( the things that make us feel good) and the spiritual things (the things God wants us to do) are real and occur in us daily. If Paul faced it, we certainly will.
The answer to this dilemma is clear. We need to learn to walk in the spirit. That means, we make our decisions, choices and plans in a way that always aims to please God and do His will. We approach difficult decisions with prayer. We seek good godly counselor of older and wiser people before we jump in to what could be a destructive scenario.
This week, ask God what He wants for you in your daily activities. Ask for His guidance and His peace so that you can hear the still small voice of His reason. If you seek His way first you can avoid a whole lot of spiritual heartburn later.