In the new testament, we are no longer obliged to bring the sacrifice of flesh in terms of killing animals or grains as described by this scripture which is one of many in the old testament:
Numbers 28:1-8 (The Lord said to Moses, 2 “Give this command to the Israelites and say to them: ‘Make sure that you present to me at the appointed time my food offerings, as an aroma pleasing to me.’ 3 Say to them: ‘This is the food offering you are to present to the Lord: two lambs a year old without defect, as a regular burnt offering each day. 4 Offer one lamb in the morning and the other at twilight, 5 together with a grain offering of a tenth of an ephah of the finest flour mixed with a quarter of a hin of oil from pressed olives. 6 This is the regular burnt offering instituted at Mount Sinai as a pleasing aroma, a food offering presented to the Lord. 7 The accompanying drink offering is to be a quarter of a hin of fermented drink with each lamb. Pour out the drink offering to the Lord at the sanctuary. 8 Offer the second lamb at twilight, along with the same kind of grain offering and drink offering that you offer in the morning. This is a food offering, an aroma pleasing to the Lord).
One of the new modes of offering is the sacrifice of our lips as explained in Hebrews 13:15-16. It also mentions that it is to be continually. In addition to this it encourages us not to forget doing good. See my previous post on praise Him continually.
A sacrifice because we are doing it even though we may not feel like, the situation around us may not look promising enough for an attitude of praise but praise Him anyway as demanded.
Why, you may ask? it is because another part of the Word says that God dwells in the midst of praises. Ps 22:3. If someone makes his or herself present when I am doing something, it follows that I can freely ask them to do things for me. They can also ask me to do things for them.
All of this can only happen because I am developing a relationship through speaking and listening.