That God's love towards us does not fluctuate is a truth many of us take for granted. Why God's love never changes is because He never changes (Mal.3:6). He is not given to whims or fancies. Once He has chosen to love us, He says that He will never forsake us (He.13:5), which means He never stops loving us. His love towards us is also called 'everlasting love' (Je.31:3). But even though this truth is so well-known to us, why do we still find ourselves doubting it at different times?
It may be because we think God is just like one of us (Ps.50:21). We are subject to many types of changes. Things that happen to us have a tendency to make us think, feel and behave differently. What people do to us can provoke us to respond differently. Changes in our biochemistry can affect our mind to warp our thoughts and behaviour. Even a change in the weather can affect our mood! Because we are like this and we are used to seeing other people like this, it is natural to think God is also like this. But He isn't!
God's behaviour comes from who and what He is. He is not fickle-minded and He is not pushed around by circumstances or different people. He is the only One like that. On our part, we ought to become like that, but the fact is that we aren't there yet. The more we grow in that direction, the better we are able to appreciate the fact that God is unchanging. "Jesus Christ is the same yesterday and today and forever" (He.13:8).
God knows how fickle we are, and He takes that always into consideration in His approach towards us. He overlooks our minor ups and downs graciously and generously with a large heart, and is not nit-picking to point out every mistake we make. This should be very comforting to us to know, and so we mustn't get worried about His relationship every time we realise we have slipped up. God knows how fragile we are, and He treats us as a loving Father who knows we are made of dust (Ps.103:13,14).
Of course, this doesn't mean that He ignores it when we move away from Him going after other things that can take His place in our hearts. He monitors our heart's direction, and that is very important to Him because that is where we have our values (Pr.4:23). This is not about momentary fluctuations but our choosing to deviate into a path that will take us away from Him. He is jealous over us that He doesn't want us to be deceived by anything that appears to be attractive to us in the short term but whose end is destruction. If we ignore His warnings at this point and venture out too much in a wrong direction He is even willing to inflict pain on us in the form of discipline (He.12:11) so that we may turn back to Him. That too is a mark of His unchanging love towards us.
We need to be 'grounded' in the knowledge of this love (Ep.3:17,18) so that we may not waver when we cannot understand the different experiences we go through, holding on by faith to the truth that our Father's love for us never changes or ceases.